yellowing leaves: heat stress? nutrient/ph problem? (100% perlite grow)

Hello,

Recently acquired 4 plants (blueberry) at each around 6(?) weeks veg growth (about 2 feet tall). They were previously grown in coco/soil mix, I think? Re-potted them in 100% perlite, and fed them with Optimum Bloom (Hard Water) A&B (Growth Technology).

At the same time, I acquired some seedlings (of another strain) in rockwool cubes, which I re-potted into perlite, and also watered/fed the same Optimum Bloom solution.

As lights went out, I misted them both with Plant Vitality.

Two days later, leaves on the 4 big plants started turning yellow, from the bottom up. The next day, (3 days after initial nute watering), I gave them only water (no nutes). More and more leaves keep turning yellow on the big plants, until today (approx 1 week later), about half the leaves on all 4 plants have turned bright pale yellow. From the bottom up about half way. (each day the yellowing of the leaves gets higher)

The other little plants haven't been affected.

This is a very new set-up (first time growing like this -- previously used soil and natural light), and the grow tent is very very hot. The temps are between 93-97f with the light on (600w). Extractor fan seems to be pulling hot air out, but passive air intake doesn't seem to be bringing in enough cooler air. (I know this is a problem which needs to be addressed!)

I'm wondering if the yellow leaves are due to overall heat stress? The very tops of the plants are still green (so, probably not heat burn from the light). Just going yellow about half way down, to the bottom. This makes me think it might be a nutrient problem?
Another thing -- when I first got them, the leaves were all very dark green. Now the even the (non-yellow) green leaves all seem a bit paler (not as 'deep green' as they used to be).

Also, I tested the ph of the water, and it's really high (8.0). Could the yellow leaves be related to this?

(the photo attached was taken a couple days ago. Since then, the number of yellow leaves have almost doubled. Today I removed many of the yellow leaves, and watered all the plants (with the same Optimum Bloom solution) as I did in the beginning. I thought maybe the big plants were in shock from being re-planted into a different medium, and also by using different nutrients?)

Any ideas on what could be the problem(s)?
Thanks!
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kamut

Active Member
I don't think your attachment is working, but that's okay. It's good that you are tracking the direction of yellowing. Bottom to top is mobile nutrients: N, P, K, and Mg (is there another one?). Sounds like an N deficiency. Your ph is too high. Soil should be about 6.5, hydro 5.5. The high ph is locking out your N IMO.
1. Foliar feed your plants to stop the deficiency. Your nutes probably have directions for making a foliar spray. Do pretty frequent foliar feedings with something that is 'complete' (NPK+trace minerals). Fox Farm veg formula is good if you don't have a nute solution that has all that. Your plants can eat through their leaves when they can't eat other ways-this is kinda like getting an IV of saline/glucose when you go the ER.
2. Get that ph down with a 'ph down' product or start using Reverse Osmosis water or something if your water is coming out of the tap at 8. If it comes out of the tap at 8, the water is no bueno.
3. Get the Jorge Cervantes book. It covers the fundamentals. The internet is free, but it's too hard to learn things piecemeal IMO.
4. Don't give up, try to stay calm. The most productive growers were all newbs once.
 
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