To me it looks like your plant is going through transpiration. (trying to get rid of moisture).

Possible problems:

Light is too close (optimal distance is 18 inches from tops).
Room temperature is above 80F.
The fans blowing too much air.


Too much wind for prolonged periods can start to dry out the leaves. The first stage is for the plant to reduce surface area and that requires they curl. If heat is involved they curl up because the stomatas are on the bottom and that's where plants sweat (transpire) the most from. If they were to curl down they would block the stomatas and hinder their ability to transpire and cause them to dry out faster. Eventually the leaf will die unless steps are taken. It's also a good bet that if one leaf is affected more are too. Your pictures show this. Raise your light and reduce the direct air contact and see if it helps.

Other than that, your plant looks very healthy.

It is not a nute problem.