HARVESTING TIME when to flush nutes?

[Bspectral]

i know that the average time to flush out the nutes with straight ph adjusted water is about 2 weeks before harvest.....

but my question is when do you know when you are 2 weeks from harvesting? are there any signs in the bud on when you change over your REZ with ph adjusted water? thanks

i just started the flush into 5 weeks flowering so ur buds should look similar to this when u do urs'''''about 10-25% of the pistols are changing to a brownish-red