Judging by the current size with 4 weeks remaining. I would say to just continue what you are doing.Stop feeding about 10 days before harvest date and flush with water. With 4 weeks remaining those buds are gonna swell and take off like you wouldnt believe. I get that "o crap my plant isnt gonna yield syndrome" at about the same time. Then i remember patience. And that a plant packs on most of it weight in the last few weeks.