Do white hairs turn into brown quickly?

I usually go by the basic rule if 75 percent of hairs turn brown/orange , you have around 2 weeks left. Unless it's an auto , they can change quite quickly .

Why don't you have a diary? We don't even know WHAT you're growing, how LONG they've been growing, we know NOTHING about your specific grow except for these two pictures. But the pictures alone tell us you should not even be contemplating flushing at this point... they're not ready. Not at all. Good luck...

You still have 3 weeks or more to go, start flushing when there are roughly 95% brown pistils and harvest 7-14 days later when there are 98-99% brown pistils. This will put you in the "10-30% amber trichome" zone, without having to look too closely. At this stage, you still need to keep on with the feeding.

Keep feeding you are in heavy bulking. Don't go off a package dates. Stop feeding when pistils are mostly brown and do a flush and fade. You got about 1 to 2 weeks of feeding left. Heavy potassium and phosphorus for the bud development is recommended.