Curling leaf tips on 1

My photo (only 1 of 4) purple Frost Giant is in week 6 of flower, just flushed today w/ FF sledgehammer. Tips of uppermost leaves curling up. Otherwise looks good, buds filling out nicely. What do you think?

Hard to really tell without better photos.
Maybe use your flash to give a better natural look.
Leaf tip curl is sometimes heat, excess light, or it may be too much nitrogen.