Heat stress? recovery time?

I have 12 plants in an ebb and flow bucket system, with about 4 different strains.

I've had my lights pretty close to the plants, and they seemed to be doing fine, but now one of the strains seems to have heat stress from what I can tell..

The leaves are very rigid looking like a potato chip.. is this from the lights having been too close? Or could it be from something else?

If in fact it was from the lights being too close, how long will it take the leaves to start looking normal again, now that I've moved the lights further away?

Thanks.

well once the leaf burns, its burnt. its not coming back. not to worry tho, there will be more leaves growing.

a pic would help mate, are they burnt at all? if not, dont worry had a few that looked like they had an hard on.

No burnt leaves, they just look rigid like potato chips, rather than smooth.. So im assuming it was most likely from heat stress, and wondered how long it would take for them to go back to looking normal.. Unless this is a symptom of another problem, like a nutrient deficiency, etc...

Are there any other problems such as a specific nutrient deficiency that causes the leaves to become rigid looking like potato chips?