What do ya think about these leaves?

What do ya think abot this leaf, never seen this before and have a few now. I'm growing in rockwool drain to waste. No nob before, doing well... wondering if my ph meter is off... or maybe heat stress from lights too close?

What do ya think?

Any more info ?? Lights area ventilation medium??

Heat stress deluxe.

Yeah... I'm thinking heat stress is a def possibility. Room is good at 78*, but they grow way too tall, getting pretty close to the lights, so maybe... but overall plants look nice and healthy, I'll have to take another pic soon to show very healthy overall growth.

I'm growing in rockwool so I'm also wondering if maybe there's any way its because the media has dry pockets/dryback is too much

I did recently stop "conditioning" the blocks because apparently you don't have to condition grodan any more (i confirmed this with them, but they recommend a sink/soak to ensure no dry pockets which I didn't do the last few rounds)

Any more input with that info?

Like I said I also wonder if my ph probe is fucked bc it's pretty old, even though I celebrate it... but I'm juuuuuust about to move into a new facility where all equipment will be new... so not trying to buy a new probe 1-2 months before the move if I'm not sure

General hydroponics, bluelab, Hanna, just about everyone has a calibration solution or four.
Just check the damn thing, a faulty tool is no good...

Looking like some really hardcore heat stress. You can get a cheap-o PH meter from amazon for 10-15$. Might be a good tool to have until the move.

Nope, finally figured it out... detective batches of grodan rockwool... I guess they have a new manufacturer in canada and they fucked it up royally. Think it's something to do with ph instability that's specificity from the defective rockwool.

Slimjimham said:

Nope, finally figured it out... detective batches of grodan rockwool... I guess they have a new manufacturer in canada and they fucked it up royally. Think it's something to do with ph instability that's specificity from the defective rockwool.

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That’s heat stress

Lordhooha said:

That’s heat stress

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Nope he is correct it’s caused by the grodan rockwool new cubes doing that for whatever reason

1st thing i learnt was ph meters suck dick and need to be calibrated every 2 weeks maybe not that often for a good branded ph meter but for them cheap ones calibrate weekly 2 weeks max
having to second guess your ph is a very unpleasant feeling
2nd thing changing your res is important the second you start seeing problems best not to wait in hydro as plants can go from good to shit in a few days of bad ph or too much ppm
im new with hydro but by fallowing then 2 things it has improved my grow and has prevented any big problems

instability that's specificity from the defective rockwool?? cant you just flush it rockwool shouldn't retain allot of stuff. i am considering flood and drain with rockwool over doing dwc so some information on this defective rockwool would be good for future reference

iLUVOG said:

Nope he is correct it’s caused by the grodan rockwool new cubes doing that for whatever reason

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Well you may want to read this and compare and contrast to his. He’s getting into the high end of heat stress most cases are mild.
https://www.growweedeasy.com/heat-light-stress