Does anyone have an opinion on what this could be?

Plants are growing wonderfully, except for this sort of "wrinkling" or "cupping" around the edges. Anyone know what sort of things could be causing this?

heat...........

Might be a little warm temp-wise but...

No one is going to offer you any advice, even half-assed advice, with a yellow picture and ZERO information what you got going on. At least nobody with half a clue what MIGHT be going on. So expext answers from nobody or answers from teenagers whol still have no answer.

Looks like heat to me too.

raise your light a bit,see if that helps.