Possible heat stress? Only when nearer to end of light cycle. Pics included.

shawnery said:

86 degrees is pretty hot.
38 humidity is pretty low.

Together these will definitely cause issues with heat strees and vpd(vapor pressure deficit).

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goatlicker said:

Hey guys,. so i lowered my lights from 18inch to 14inch the other day and noticed they looked like heat stress the next morning before the lights turned off.
I took the light up to 16inch and tried again last night but this morning they're quite bad again so have taken them back to 18inch.
The temps never really changed at the plant height, and its only affecting 2 plants, third seems to be sweet.

First Photo shows just as lights turn on, and the rest are from this morning.

Main question is.. is this definitely heat stress or light stress?
And will they recover with the light back at 18 inches now? and should i just leave it at 18inh, Its a 400w MH.

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hotrodharley said:

Heat stress. Raise the light more. Get air moving.

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goatlicker said:

Yeah i figured, it happened straight after i moved the lights, I have them back up at what they were at (18Inch)
Will the recover and go back to normal or just stay like that?
So that means i can't lower my lights lower than 18 inch?
I tried 14 and 16 and they both made them canoe.
I have a 2 small fans blowing air around, between the light and plants.

Updated pic of them now the lights just turned on.

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hotrodharley said:

I can't get mine any closer except with an air cooled reflector. My 600 watt HPS can be about a foot away in the air cooled. My 400 watt no less than 18" or heat stress. It's not cooled.

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goatlicker said:

Ah thanks, that makes me feel a bit better.
Ill keep it at 18, it seems to be fine at that.
Hopefully that fixes it, Will those leaves go back to normal?

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hotrodharley said:

They should. They just do that to dissipate heat. Give a bit of cal mag. Stress increases calcium use by the plant.

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