when you are watering, do you just add water to the plant or do you flush the plant? It looks like a pH thing to me, if it was nute's you would see the tips of the fan leaf curl'd down and brown/dried..... there are couple of testers out there that will let you test the pH of your soil and see what nute's you have there as well. If you havent flushed your plants, i would do that right away...