Using cfls, temps between 65-75f, Fan for vent and air circ, Feeding small amounts of 24-8-14 when watering. I water every 4 days or so. My question is a few fan leaves towards the top, but not the top, are showing these small dead tissue just on the edges of the leaves. No where else. Bout 4 large fan leaves. It's almost like someone just dotted them with a crude marker or something. The color of the patches is a dark brown almost black. Anything to worry about??? Has this happened to anyone else?