Not quite, wait until 90-95% of the pistils have turned brown.
If you prefer a heavy and sleepy type of body stone, wait until practically all pistils have turned brown.
Harvesting while there are still some white pistils will give you a more trippy and psychoactive mind warping high, due to the higher THC content in flowers with some remaining white pistils, rather than flowers that have higher levels of CBD and CBN, due to THC break down, which occurs once the plant has passed the peak of its "ripeness", as indicated by all the pistils being brown.
So it depends on which type of effect you prefer, a head trip or a body stone, but either way, you still have around another 2 weeks or more before harvest, so starting flushing now would be a bit premature. Giving just plain water for the last 7-10 days before harvest is usually more than adequate for a flush.
Hope this helps,..........
Organoman.