I am only week 4 into my flowering stage. I noticed some of my pistils are turning brown. Its not in one specific area. I notice some at the bottom, the middle, and close to the top. I only have 2 plants, and they are both females, only. I have them under a 600w HPS I have them under a strict 12/12 cycle. Digital timer. 72-75 Degrees I feed them twice a day. Gen Hyd flora series Big bud formula I keep the light atleast 12 inches away Any thoughts?