Plentiful Sites but Micro Buds

It’s your light penetration. The buds on the bottom don’t receive any light so they are essentially just stealing nutrients from the prime buds up top. If you look at your picture you can see the light only goes down into 1/2 of your total canopy height. Just start low and start taking little side shoots and the big leaves until you can see just a little light coming through the bottom. Will definitely plump the tops up and prevent problems down the road. Happy Growing!