You should tie the tall ones down or you will run out of room. Just tie from the top and loop it down carefully.. tie it back to your pot. I use Green Cure for powdery mildew. Its not very expensive and works well. As far as bud production goes, it looks like your at about week 2-3. Fight off the PM now before you get deeper into flower. If you spray late into flower your risking mold and tainted buds. Increased air flow will help quite a bit. Get a nice fan in there and a better exhaust fan. ..For next run, read up on "topping." There are some good threads on here. On a positive note, good job not burning your plants. Its easy for new growers to burn their plants especially with Dutch Master.