Under the circumstances mate, it's hard to judge exactly when they will finish, if your talking trich colours. Whispy is looking both the best and fursthest to go plant to me, a bit longer than 2. 3 is your first finisher, 4 & 6 not far behind. Have you got the required magnifier/microscope? I use 100X microscope to make sure. If your in doubt, I'd say, leave it 3 weeks, and take 3 & 6, give it another week and take 4, another and take 1 and whispy. due to all the flushing that has taken place, your ok to feed up to 2 weeks before harvest and just stop, no more flushes. No water either for the last 3 days. No heat last day.