What I would do if I were you is to take a small clipping of one of your more mature buds quick dry it and smoke it. It will not taste good but it will tell you if your happy with the high. If you are happy then start the flush If not wait another week and try again. Remember you want most of your hairs to be darkened otherwise they are still growing and getting fatter by the day you don't want to lose yield.
when you start your flush you will only feed plain Ph'ed water no nutrients at all. This is to let the plant use up all the extra nutrients contained in the plant so that there is none left when you harvest. This is so your buds don't taste like chemicals. It needs to be for at least two weeks, if you want the best flavor from them.
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How about I tag the experts i rely on
@JAYAR and
@Waximus I know they can explain better then me.