You should flush when they look almost finished, you gotta observ at the trichomes and also the general look of the plant.
Trichomes should be well formed and milky when u flush, the pistils use to be almost all brown at this point. Plant should look like its autum in there. You have 7-14 days from flush to pick the right moment to finally cut them down.
Only the plant will tell you when to do it, but il would say you gotta wait at least 2-3 more weeks before flush.
Good luck, and sweet smokes