Looking at the leaves I'd say just feed a reduced strength feed if you're set on flushing. There's definitely a deficiency issue and not knowing what you have been feeding and more details it's hard to say why. My best guess is a P deficiency but I'd keep feeding until harvest. Flushing is fine if the plants are healthy but if you're already facing a deficiency it's not going to help. I personally like green healthy leaves up to the chop. As far as when to chop. I'd look more at the overall appearance of the buds and worry less about trichome color. You can always do a partial harvest of the tops and leave the secondary buds a little longer to ripen. That's how I got used to where I want to harvest. I chopped way too early by looking at trichomes in my opinion. Since changing to visual cues like swollen calyxes, buds bending over to the ground and most if not all pistils browning, I've been way happier with my harvest times.
