Thanks everyone. It now seems this issue is affecting all my other plants as well. When this first happened I was using 20-20-20, but the leaves were already turning yellow. And so with some research I decided to give my ladies Fox Farm. Since the plants are already flowering I followed a schedule that started at week 5, Big Bloom, Tiger Bloom & Sesame. Am I correct in doing so? If a nute deficiency would it be wise to also use Grow Big? If yes how much, how often and for how long? The leaves started turning yellow only around the edge and then spread inward if that is any help. Please help, I am a newbe and am completely lost.