Mystery Grow Question - When is it Done?

Beyond the 8th week flowering on some mystery female bag seeds in a bubbleponic setup. Must of the colas / budsites tops have young white tendrils still - others hairs/tendrils have gone all brown. Is that a good indicator as to when its probably done its thing?

Also - to leave it under the lights an additional 1-2 weeks past its ready time - can the buds grow further? Or is it best to pick them when theyre just right timewise?

What would happen if you went with a grow-heavy formula in the 8th week, with GH FLora series. Any chance the last bit of bud growth would get chunkier?