Light stress??? Just seeing the leaf edges standing up has me abit concerned. Light is running at 25% I did have it on 50% until a few days ago.

guesstimate your DLI could help eliminate that possibility. could be heat / light but plants look fine. They are almost reaching too much for the light. might be able to give a bit more. Bump K 5 % think that's one of the symptoms with the tips .. though i'd wait for that hint of tip discoloration to progress further along tips of leaves before going that route. several things start out that way.