Ok, yes I have a BS in plant science. I work in the horticulture field. And
@pop22 is famous for being against flushing, I happen to agree with him fully.
From a plant physiology perspective:
Leaf senescence is best explained by fall leaf colors. When the reproductive stage is nearing completion, and the environmental variables start towards fall the process called senescence starts. The plant begins to scavenge all it's nutrients stores throughout the plant and send it to reproductive and energy storage compounds. All mobile nutrients are reassigned. The leaves usually turn color because the plant is getting ready for dormancy or death. In cannabis, it knows it is about to die, so it pulls those nutrients to reproductive systems.
So flushing triggers this system early. As I understand what people want from flushing, it's a better taste to the smoke. They think because they are not adding nutes their smoke will be closer to pure. I call BS. If you want to effectivly remov nutes from the system the only way to do it is to remove leaves. Flushing will just reduce photosynthesis, reduce water uptake, slow down bud and trichome growth, and you still end up with extra minerals and stress compounds in the buds.
That's my two cents.