If she has been only flowering for 4 weeks, you are about half way through.
Start witholding nutrients (flush) when the plant has about 95-98% brown pistils and harvest about 2 weeks later when they have 98-99% brown pistils, which will put you in the "10-30% amber trichome" zone without having to look too hard.
Hey,
don't flush plants. it will only withhold nutrition from the plants and make your harvest smaller.
good smoking attributes come from curing not flushing.
in agriculture no one does it, its a myth