there is no rule .. if you're in soil try to five pure water 10 days minimum .. in hydro it can go faster
dont try to make them yellow or starve them
koolbloom, for me looks like a booster for soil, there is much P .. dont overuse it man
for the last 2 weeks in conjonction with a reduction of the main nutrient .. use a little bit, or it will accumulate in the soil/burn the plant and even 3 week flushing wont allow the plant to consume it ..