Diagnosis needed with plantlings

[desiBud420]

Hi,

This is my first grow with 2 photo females in a grow box for a little over 2.5 weeks now. I have two young ladies that are just 2.5 weeks old and sprouting nicely. I only noticed on my last topsoil water spray session that one of the plants, on it's first set of single leaves above the cotyledons, the tips of the 2 single leaves are a tiny bit yellow and maybe look like they're curling a bit downwards. Both tips are equally yellow and only at the bare tip.

Magnified it for a better look. Quick snap of inside grow box. 84w (400w output white light), and a new addition lately for a slight range of color wavelength with a 20w (100w output light). I figure I have 500watt output in total which should be enough at 2-4 inches. I also thought to wait until the plants got into the 3rd week to push their watt limits for stronger growth in these light wavelengths for my budget so I only had the 85w cfl to start with, which did fine earlier.

My questions revolve around a bit of my own diagnosis and question as follows:

1) are the lights too close or has addition of 20w bulb recently added too much light, or is 2 inches too short at this point in grow?. I feel it's light burn even though the airflow inside is pretty good, a bit more than necessary I feel with a 120x120x38mm PC fan with airflow of 115cfm (no dimmer attached). Note I can keep my hand right above the plant and not feel any burn or discomfort at the 1.5-2 inches distance between cfls and plant tops. I Rotate the pots every few hours and make sure they get a 360 spin throughout the 18 hour light cycle and move them between each other and exchange spots once per day. There was no problem before the 20w warm light, and the other plant is also blooming, but no early tip yellowing on that one. Both have same soil and spray/watering feeds the same (or rarely when extra needed). Different strains so I guess that factors in as well.

2) soil pH is set after watering with about 6.7-7 pH according to pH strips I got. I don't like their accuracy but are eSier to use and throw unlike maintaining electronic pH detectors with pH balance solution, which I can't get readily available here, but quite high maintainence for my taste. I Added limestone sprinkle to soilless, organic dry manure, and peatmoss at the time of potting the germed seedling. . Ratio 1/1/2 ... Can't get vermiculite/perlite here so I make do. No nutes till 4th week unless a deficiency occurs, which I fear at this point early in the grow.

3) grow box temp wanders from 25-27'C (77-83'F) depending on time of day/night and I actively use my a/c to stabilise the heat from the cfls as does the speedy PC fan together. Again I feel the pull is a bit more than necessary and not sure how to slow it down without a dimmer or some filter material to cover my air intake flaps with. This is the model I have jammed in there.

4) if anything else this also looks like the pre-signs of a Nitrogen or Copper deficiency, or is it light burn to me.

So temp, water/soil pH, airflow, lights and nutrients. Who is the culprit if not a combo?

I thought it's better to get some logical opinions while I can catch a deficiency in it's initial stages.

 

[landfarmer]

How big are those pots there in? If thats a dixie cup or something make sure its not root bound and ur getting good drainage but if thats good it Looks like nutrient issue.

 

[desiBud420]

How big are those pots there in? If thats a dixie cup or something make sure its not root bound and ur getting good drainage but if thats good it Looks like nutrient issue.

Hi landfarmer!

The pots are 4 inches in height and 3.5 across. Drainage is good. Punched structured holes equally symmetrical underneath and on the bottom/sides as well. Drains well when watering.

I'm not sure if it's root bound yet (2.5 weeks since sprout),but I thought to transplant into a 3 Gal container by next week. Would the roots have developed that quickly to get root bound in 2.5 weeks at such a small plant?

If this a nutrient deficiency, as opposed to toxicity, I have some nutes lying around called Grow More 20-20-20 if need be. Avoiding nutes intentionally to avoid killing them early and just being patient

 

[landfarmer]

Depending on how well its watered it can cause the root to bound on the bottom of the pit instead of filling the whole pot. I would start a light nute to see if that would eliminate the issue, but the issue doesnt look to bad ive had way worse on my plants and they always bounced back

 

[desiBud420]

Depending on how well its watered it can cause the root to bound on the bottom of the pit instead of filling the whole pot. I would start a light nute to see if that would eliminate the issue, but the issue doesnt look to bad ive had way worse on my plants and they always bounced back

Thanks champ!

It was last watered Friday 18th in the evening. During that time I've sprayed the soil tops mildly with a mist spray whenever top soil was dry and crispy? The PC fan has a 115 cfm and pulls a bit of air in my 1.6x1.8x2' grow box which pulls more air than I think is necessary.

I'll try a very light nute watering to the black Indica that's got the leaf problem. I'll leave the other one alone since there's nothing weird going on with that one, crown royale. CR is booming in height and leaf growth as compared to the BI.

I germinated both at the same time, and the BI tap rooted first, CR's tap root came a day later but has overtaken the BI in overall growth and progress up till now. the crown royale serves as a good indicator so I conclude and agree with you that this is a nute issue. The black Indica probably needs more nutes at this point than the crown royale and by the looks of it it's a nitrogen deficiency. The tips are still the same and haven't degraded yet though.. I'll give it another day max and give the little bugger some light nutes.

Cheers.

 

[desiBud420]

Ok I'm back. I've got 2 opposing opinions and solutions as a result, and I'm not sure which can be deduced to the correct diagnosis/solution.

Today the cotyledons on my black Indica started turning a mild yellow starting from tips and curling downwards (curling set in 2-3 days ago). The first leaves above cotyledons already have the tips yellow, but has not progressed further in degradation. Those yellows are much smaller in surface area compared to cotyledons. The indicas height seems stunted when compared to its crown royale that sprouted a day after and has taken the lead in growth, both at 2.6 weeks.

I feel (black Indica) is either:
1) stunted and pH is maybe off locking out nutrients leading to a deficiency?
2) Or it's a simple nute def.minus the pH of water/soil. I'm gonna test this shortly and update stats on soil/water pH.

Any other suggestions pls let me know somebody, I want to catch the bastard before it spreads in my plantling!!