I used to feed and plain water alternatively and then flushed for a week before chop and had no problems and may have missed out on yield, but I didn't have the time to experiment as too much was going on in normal life
Also growing in hempy first grow, 2.5 weeks into flower. I've read alot on the subject lately, don't flush. Unless u are overfeeding them there is no problem and u can just forget all about harvest flush and focus on other things.
There is no evidence it's doing any good for the plant. Sure u can turn down the strength very close to harvest and save a tiny bit of money, but that is all it will do.