Hey there if you want bigger buds then you need PK boosters. Your potassium and phosphorous are what build your flowers. I dont see the nutrients listed that you are using so it is hard to recommend a specific booster. Your plant looks great. The only issue I see is your plant is a little heavy on the nitrogen. The clawing on the end of the leaves and the burned tips along with the dark green color show this. I would back off of the grow nutrients you are using and switch to flower nutrients. It will help build buds.