Tragedy Strikes - Advice Welcome

[sammysnake]

In the last stretch of my first hydroponic grow and I unfortunately have encountered a pretty serious looking plant problem. See picture below:

Background:
- I use tap water ~150ppm as the source for my reserviour.
- Keep pH around the 6.0 mark.
- GH nutrients, kept in the 700-800ppm range.
- 1x 300W LED, 1x 400W MH
- 4 weeks into flowering
- No obvious plant problems up until this point besides more previous issues with LED light being too close

Places where I know I've gone wrong recently that could be sources of plant issues:
- A few times I've gotten lazy and let the reserviour levels drop too low causing the ppm to shoot into 900-1000 range.
- Have the LED 300w too close (12", running out of vertical room or would have it higher)

Additional info:
- There was a direct correlation observed that the spotting was occurring within the sweet spot of the 300W LED light.
- Has happened previously but to such a drastic extent and not on colas, only lower growth

My own hypothesis (from my reading online):
- Spotting looks close to Cal Mag deficiencies, but shouldn't be an issue with tap water, only RO
- Could possibly be pH related, I only have been relying on pH colour indicator for analysis (room for error). Has been fairly close to 6.0+- 0.2.

- The main source of issue I believe is a combination of letting the nutrient ppm get too high and stress of having the LED light too close. The only problem is this current hypothesis doesn't fit with Cal Mag deficiency symptoms.

So my questions are, could a nutrient ppm spike + light stress manifest itself as a Cal Mag deficiency? Should I be supplementing with Cal Mag just incase, even though I use tap water?

Current plan of action is to keep on top topped off reserviour levels to avoid ppm spikes. Also I have done some musical chairs in the room to get a smaller plant under the LED light so it is not as close to the light.

 

[DukeO]

What do your roots look like?

My guess would be you have a PH or root issue.

It is very hard to get a good read out from the strips and that could led to a nute lock out.

What is your rez temp?

 

[sammysnake]

I use pH indicator solution, which is slightly better than strips, ya?
Reservior Temp: 21.7C / 71F
Roots are good (pretty sure colour is just from nutrient solution):

I am going to agree on a pH issue.

 

[Icemann420]

To me the roots look really damaged I believe the color is from the nute but they just have that broken poky look not fresh and soft. A 71* Rez temp is a good breaking ground for root rot low to mid 60 keep the root at minimal. And try to keep the Rez filled at all times. Ad also try better water at a ppm of 150 to start off at is pretty high. If change the Rez with fresh ro water add your micro,grow, bloom,Calmag then your additives and add some grate white or z7 she will b a lot happier


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[sammysnake]

Not doing DWC, from my reading root rot is not as common when drip method is used. Roots might also have a different appearance because it is not DWC. This is just conjecture though, you may be right.

The area of damage is localized, it was just in this zone of intense LED light that the issue presented itself. I am wary of changing reserviour strategy to RO at this point. The problem does not seem to be getting worse now that I have changed up the lighting a little bit and have been keeping up tighter watch on the reserviour.

Overall the plant seems to be doing good:

I have kind of come to the conclusion that it is a reserviour pH / nutrient ppm / light stress issue. Thanks for chiming in!

 

[Icemann420]

Well good luck I really hope it works out for u the plants look close it would b horrible for it to go south now good luck


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