White Widow problem

My plants are almost 3 weeks old and on 1 of them the leaves are starting to curl on the side, was wondering if this is a problem??

heat stress.

cheers for the diagnosis, what do U suggest I do?

if ur temps are high then lower them.
if ur lights are too low, just raise 'em up a bit.
some plants just show heat stress quicker then others, some in the room wont show anything,..even sister plants.
The other thing that (highly doubtful) it could be is the beggining of over-fert,.whereas if the whole leaf continues to curl in and 'canoe' then get crispy and die..

but if i could have any problem, itd be heat stress, easy fix

Thanks for the reply! Yeh I think it was heat stress since I havent started using nutes yet. I also raised the humidity a bit up to 60/70 as it was dipping into the 50s. Also raised the light up a couple inches.