Flush ? ... harvest? they changed overnight white to amber...

When you are checking out Trichomes make sure you are not reading off a leaf, and are looking dead-on in a bud, the trichomes on leaves amber faster, I like to be at about 80/90% Milky with about 5% Ambers but that is just me, my wife likes more ambers, to flush or not to flush, misconception in my opinion, when I hear flush, I think of folks pouring massive water through the substrate to rinse out salt-based chemical nutrients, something to also help lower PH, growing organically like you are doing and using BioBiz to control the microbial life in your soil, I would not flush, for me the last few weeks I tend to move away from BioBiz, and just feed H20 PH at around 6.2 sometimes adding a small amount of BioBiz Fish Mix, your soil is loaded with life and for some Autoflowers, less is more. I feel you have about another week left, your spec on this is Flowering 49 - 56 days / give or take.