Leaf problem

see photo,

alot of the new leaves on my plants and also on my friends plants in different grow rooms but still clones from the same mother. are looking a bit sad at first I thought it was a heat problem but even leaves at the bottom of the plants are doing the same thing kind of krinkled up but not dry or yellow. any ideas?

It might be heat or it could be ph. Do you ph the water? And whats the temps of the grow room.

hi, I always ph the water, the grow room is aways between 26 - 29 degrees celcius, have constant fresh air cirulating inlet and exhaust.