Leaves Curl Inward?

Here is some pics of a friends plants the leaves curl inward , Not the tips the whole leaf please look at my Pictures and post your opionion ,He has 9 plants going all look great just this one does this , all fed the same and watered the same ,the strain is the same ???Help

Hmm..I think the 'eagle claw' is usually too much N, but if you fed them all the same that kinda seems unlikely.
Maybe a good flush would help(?).

One of mine looks like that, think mine is heat. It is a little taller than the others.