my plants that are in bigger bags have smaller buds!

my 20 gallon bag plants are ready to b chopped...i've got 2 in 37 gallon bags that aren't ready and have no where near the amount of bud on the plants in the smaller bags! i'm gonna let em keep going for another week or so, but i don't think they will bulk up anywhere near the size of the plants in the 20 gallon bags. anyone ever had anything like this happen?

Maybe the soil is to dense for the larger bags and is not offering enough air flow to the roots.