hey man,
if you are just 2.5 weeks into flower i wouldn't worry bout bud size yet. you still have a while and they will fatten up as the plant grows. you can try using bud candy or gravity. both can be purchased at hydro stores, or just use unsulphered blackstrap mollasses with every other watering or so. the last 2 weeks the buds will fatten up the most. good luck hope that helped.
peace