Yellow tips on new growth - What's causing this?

[Acid]

So I've tried looking this up everywhere, lots of people always mention nutrient burn, but the nutrient burn I know is brown, not yellow & spreading.

Here are some images:

This has been going on for ~1 week now, on one of the 4 plants I have. Here are the details:

* 3.9gal Autopots
* Coco / Perlite 60/40
* Canna Coco A+B, Canna Calmag Agent, sometimes Grow Genius MSA for some extra silica
* 25% Tap, 75% RO Water
* Speedrunseeds Autoflowers
* MarsHydro FC6500-EVO at 50% on max height, only around 400PPFD currently, 24/0 cycle
* 4x4x6.5ft tent
* Oscillating fans, exhaust fans, all working normally
* Temps usually between 25-27°C, humidity 55-65%
* Apera PH60, fully calibrated weekly, but usually only off by 0.01-0.03PH. Always washed in RO water & stored in 3M KCl Solution
* Milwaukee Instruments EC pen

Feeding schedule:

* 25% Tap into 75% RO water, EC 0.1 at this point by the tapwater
* Optional at this point: Grow Genius MSA (mono silicic acid), around 0.5ml on 30L of water IF I use it, just sometimes
* Raising EC to 0.6 with Canna Calmag Agent, because any lower and I will get magnesium and calcium deficiencies on all plants
* Canna A+B until 2.0EC
* PH to 5.65 in the reservoir with Canna PH Down
* Wavemaker which keeps mixing the reservoir 4 times a day for around 15 minutes each time.
* Res temp not perfect, around 70°F, which is still okay
* Plants drink around 30L in ~4 days, at which point I discard the leftover 1/2 gallon in the res, and mix a new solution.

This symptom has been going on for around 1 week now, as mentioned above. New leaves come out with yellow tips, and no it's not "healthy new growth!", it's a problem as you can see, it doesn't disappear. Nutrient burn seems to be different, I know the brown burnt crispy tips, these tips are just bright yellow and keep looking like this, and in some cases they worsen and the yellowing spreads downwards as you can see.

I'd like to know what's going on here, if anyone has an idea! I know this problem doesn't seem dramatic for now, but I'd like to know the reason behind this in case it DOES become a big problem.

I wanna quickly mention this - They're autopots, there is no runoff and no topwatering. If I topwater, I would shoot the EC inside the coco through the roof, as a salt-layer collects on the top part of the coco. I'd have to flush heavily if needed, like REALLY heavily, I wanna make sure that there's maybe another solution to this before I risk flushing this pot.

 

[Doctor Trevor]

You're probably overfeeding them. Could also be light stress.

 

[Wastei]

So I've tried looking this up everywhere, lots of people always mention nutrient burn, but the nutrient burn I know is brown, not yellow & spreading.

Here are some images:

This has been going on for ~1 week now, on one of the 4 plants I have. Here are the details:

* 3.9gal Autopots
* Coco / Perlite 60/40
* Canna Coco A+B, Canna Calmag Agent, sometimes Grow Genius MSA for some extra silica
* 25% Tap, 75% RO Water
* Speedrunseeds Autoflowers
* MarsHydro FC6500-EVO at 50% on the highest possible point, only around 400PPFD currently, 24/0 cycle
* 4x4x6.5ft tent
* Oscillating fans, exhaust fans, all working normally
* Temps usually between 25-27°C, humidity 55-65%
* Apera PH60, fully calibrated weekly, but usually only off by 0.01-0.03PH. Always washed in RO water & stored in 3M KCl Solution
* Milwaukee Instruments EC pen

Feeding schedule:

* 25% Tap into 75% RO water, EC 0.1 at this point by the tapwater
* Optional at this point: Grow Genius MSA (mono silicic acid), around 0.5ml on 30L of water IF I use it, just sometimes
* Raising EC to 0.6 with Canna Calmag Agent, because any lower and I will get magnesium and calcium deficiencies on all plants
* Canna A+B until 2.0EC
* PH to 5.65 in the reservoir with Canna PH Down
* Wavemaker which keeps mixing the reservoir 4 times a day for around 15 minutes each time.
* Res temp not perfect, around 70°F, which is still okay

This symptom has been going on for around 1 week now, as mentioned above. New leaves come out with yellow tips, and no it's not "healthy new growth!", it's a problem as you can see, it doesn't disappear. Nutrient burn seems to be different, I know the brown burnt crispy tips, these tips are just bright yellow and keep looking like this, and in some cases they worsen and the yellowing spreads downwards as you can see.

I'd like to know what's going on here, if anyone has an idea!

I wanna quickly mention this - They're autopots, there is no runoff and no topwatering. If I topwater, I would shoot the EC inside the coco through the roof, as a salt-layer collects on the top part of the coco. I'd have to flush heavily if needed, like REALLY heavily, I wanna make sure that there's maybe another solution to this before I risk flushing this pot.

You're pHing waaaay to low for growing in soilless (peat/coir). Way to strong feed, 2.0 EC is borderline high in veg. You need to feed extremely low running coir with Autopots since you never replenish the medium with having no runoff.

You should aim for pH 6.5 on the input growing in soilless, there's a lot of bad and mixed info on this site. If I see Ca/Mg def in veg I typically raise pH to ~7.0.

Ca/Mg agent shouldn't be needed with Canna Coco since its already included in the base A + B. I've grown with Canna Coco for years in peat and Coir and 20 years ago they didn't even sell any buffering agent or "Calmag" products. It shouldn't even be needed with RO water.

Feed at least two times daily to 10-20% runoff in veg for better keeping pH and EC stable and in check. Aim for the lowest optimal nutrient strength for the highest rates of growth. Less is more when it comes to growing Cannabis!

Hope that helps!

Cheers!

 

[Acid]

You're pHing waaaay to low for growing in soilless (peat/coir).

You should aim for pH 6.5 on the input growing in soilless, there's a lot of bad and mixed info on this site. If I see Ca/Mg def in veg I typically raise pH to ~7.0.

Ca/Mg agent shouldn't be needed with Canna Coco since its already included in the base A + B. I've grown with Canna Coco for years in peat and Coir and 20 years ago they didn't even sell any buffering agent or "Calmag" products. It shouldn't even be needed with RO water.

Feed at least two times daily in veg for better keeping pH and EC stable. Aim for the lowest optimal nutrient strength for highest rates of growth. Less is more when it comes to growing Cannabis!

Hope that helps!

Cheers!

If I shoot for 6.5 in my reservoir, my plants will be dead in 2 days. My PH is at 5.65 in the Reservoir because it goes all the way to 5.8-5.9 through the tubing, then into the bases on the bottom of the pots, and then probably higher again until it reaches the substrate inside the pots. That's why I go that low, Autopot themselves recommend a PH of 5.5 when using coco.

Yes Canna Coco A+B has extra Calmag because it's a line for Coco, but I contacted Canna & their nutrient line is made for a base EC of 0.45, which I do not have with RO water. They told me to mix 25% tapwater with my RO water to stabilize it with bicarbonates, and then raise EC to 0.45 with Calmag. I had severe magnesium deficiencies with the 0.45EC base of Calmag, which I then lowered to 0.2EC as a trial attempt because I might've just been giving too much calcium with my calmag, causing magnesium to be locked out.

This is where they really started showing extreme Calcium and Magnesium deficiencies, so I raised the base EC all the way to 0.6 just with calmag, and as of that day, no more calcium or magnesium issues.

I do not feed those plants by hand, they are fed 24/7 by bottom feeding, continuously without a break, I can't really control it. Here's an image of my 4 autos in the 4x4 tent:

They all seem fine, it's just the one in the right back corner which is throwing out all those yellowish tips, and it's becoming more and more. Only on the NEWEST leaves though, that might be important. Both plants on the back left and right are the same strain, Speedrunseeds Acid Snow, and it's only one of them showing these symptoms.

 

[Wastei]

If I shoot for 6.5 in my reservoir, my plants will be dead in 2 days. My PH is at 5.65 in the Reservoir because it goes all the way to 5.8-5.9 through the tubing, then into the bases on the bottom of the pots, and then probably higher again until it reaches the substrate inside the pots. That's why I go that low, Autopot themselves recommend a PH of 5.5 when using coco.

Yes Canna Coco A+B has extra Calmag because it's a line for Coco, but I contacted Canna & their nutrient line is made for a base EC of 0.45, which I do not have with RO water. They told me to mix 25% tapwater with my RO water to stabilize it with bicarbonates, and then raise EC to 0.45 with Calmag. I had severe magnesium deficiencies with the 0.45EC base of Calmag, which I then lowered to 0.2EC as a trial attempt because I might've just been giving too much calcium with my calmag, causing magnesium to be locked out.

This is where they really started showing extreme Calcium and Magnesium deficiencies, so I raised the base EC all the way to 0.6 just with calmag, and as of that day, no more calcium or magnesium issues.

I do not feed those plants by hand, they are fed 24/7 by bottom feeding, continuously without a break, I can't really control it. Here's an image of my 4 autos in the 4x4 tent:

They all seem fine, it's just the one in the right back corner which is throwing out all those yellowish tips, and it's becoming more and more. Only on the NEWEST leaves though, that might be important. Both plants on the back left and right are the same strain, Speedrunseeds Acid Snow, and it's only one of them showing these symptoms.

As every other thread you post you already seem to have it in your head you already got everything figured out?

Go do the same thing and experience the same problems as currently then?

It's geeting old with all these threads dude!

Cheers!

 

[Acid]

As every other thread you post you already seem to have it in your head you already got everything figured out?

Go do the same thing and experience the same problems as currently then?

It's geeting old with all these threads dude!

Cheers!

This is a problem I never had, which is why I was asking. Just like in the other thread, no one found a solution until I finally found it after a year of trying everything, which was also impossible to find for others as it was bad air exchange in the room itself. I hoped that in this case, someone will probably have a simple idea as to what's going on, as my other problem was rather rare and silly, while this one is more known.

I don't know what your problem is, I just explained why I cannot feed plants in coco autopots with 6.5PH unless I wanna kill them. Go ask anyone who uses coco with autopots successfully, and they will at most use a PH of 5.8 and no higher, usually 5.6-5.7PH. Are you using autopots? If not, why are you recommending a PH completely out of range for this system? Just a honest question.

I also explained why I have to feed calmag, because I literally tested it and saw the results of low calmag input. This thread isn't even about calmag, yet you're recommending NOT adding calmag which literally destroyed my leaves in just 2 days after a trial res change with lower calmag input, and got saved by raising calmag, even though this is totally off-topic. I wish I wouldn't have to add calmag, but if I won't, they'll die. It's nice that you don't have to use it, but I tried "almost not using it", and was rewarded with a heavy calmag deficiency.

Should I follow the recommendation of one person who uses no calmag with canna a+b and RO water with literally no connection to the current problem, or follow the advice of Canna themselves and personal experience of my plants straight up destroying themselves if I lower it? You are an insanely experienced grower and I respect that, but why are you recommending to kill my plants after I mentioned that they'll literally die if I lower my calmag? I'm insanely confused about your rather attacking answer to this.

I'm not here to fight about my calmag as there's literally no problems, I'm not here to fight about how to kill plants in autopots with 6.5PH, I'm literally just asking why my new leaves grow out with yellow tips, which then worsen later on. These plants were fed with 1.6EC as of day 8 after sprout and they were 100% healthy and thriving, they still are at 1.9-2.0EC at around day 38 now, it's just one plant with bright yellow tips which do not turn brown or crispy. That's all I'm asking about.