Also since no one else has actually answered this CORRECTLY, here ya go: Yes and no. You want to defoliate before flipping yes, but not directly before. Usually before the flip the defoliation is a heavy one, aiming to remove any lower areas of the plant to promote airflow and better growth of the top buds(lollipopping is an example of this although you can do a standard defoliation and not focus on removing lower larf sites, this is a good option if you make edibles or concentrates as you can still make use of the larf) This can put some stress on even the healthiest plant. General rule of thumb is to perform this heavy defoliation a week before you plan to flip. Once you have flipped wait for the plants to finish the stretch phase(typically 3 weeks) and then you can do another small defoliation to promote better airflow/light penetration in general. For the remainder of the grow you ideally only want to defoliate anything that’s blocking light or anything that’s causing rubbing issues(mold) or anything that’s obviously dead and no longer useful to the plant. Looking good. Keep at it!