THC Bomb Auto in coco coir

Defoliation will prevent mold, it will help you to have a better control on your LST and setup a beautiful canopy. It will also increase the air-flow around your stems/buds, it will dramatically increase the speed of growth and create a more compact plant. Judging on your last pictures I'll say that defoliation is already possible, even more, it's required/highly recommended : your plants are healthy, they developed several nodes, they're bushy and it looks like some bottom branches can't get enough air & light. Go for it, keep us up to date and good luck with these beauties!

Most, if not all the stuff you can do to improve yield is done in the vegetative or stretch phase. At this point the best you can do is to not be anxious and let the plant finish. What you can do is to remember that the most weight gain happens in the final 2 weeks of flowering, so be sure not to harvest early.