When to defoliate after switching to flower?

Hi! I do the first defoliation when I switch to flowering (the same day), but only the main stems. She'll recover from the stress in the same time she realized the photoperiod change. Then, I do it again 2~3 weeks later, when I add guano powder to the soil (more phosphorus for more flowers). But as Fempkid told you, your plants must be in a good shape to support that kind of stress.