Mid leaves are curling under

Hey guys, I need some input as to what may be the issue. I have three white widow plants in a small grow personal grow environment, and its the 5th week into flowering. I use fox farm hydro nutrients, the plants get watered every other 15min for 12 hours. Is this to much should it be once every hour? Here's a picture of what I'm taking about.

pic? and from what your explaining it sounds as if it could be over nute but we would need a pic and to know what your set up is