Check the underside of the leaf for spider mites.

What Ph are you using. You could have another problem as well like a nutrient moble or immoble problem.

No the your flour light will not burn them. they don't put out enough light to cause that type of dammage.
Zandor Reviewed by Zandor on . Leaf tips curling up - dehydration? Hey guys, haven't received any feedback in the plant problems forum yet so I'll bring it to the real experts here in they hydro section.;) Some of my leaf tips are curling upwards. They look dried at the tips and feel dry to the touch. In addition, there are some discolorations on some of the leaves, not yellow or brown, just lighter/dryer shade of green. Almost as if the top layer of "skin" was peeled away...(bugs?) Other than that the plants look great. The roots look & smell Rating: 5