plants lookin good buddy but why do u need to flush? i have an old school organic soil grow and i don bother flushing although i will just give them water maybe once a week instead of feeding them, this is just to clear any salt/nute build up. i only flush if theres obvious signs of problems, i.e leaves yellowing, slow growth pattern etc. although thats only coz i use organic nutes. as for when to harvest i'm of the belief that when u think theyre ready give them another week.