honestly, I just planted 3 germinated seeds in 8inch pots, and all 3 popped within 2 days. They are all doing great. So, if I was to guess, something else was going on besides the container size. Maybe you let the soil dry out, or santa clause came early and snatched them up so you would be "good" this year. You could have over watered, or burnt the roots while placing them in the soil, roots don't like light.

OR maybe the siren guys/popo's/umm those dudes with badges came and gave you a christmas gift by taking all those seeds out so you wouldn't be charged with intent to sell........MAYBE I'm smoking something other than weed, but, the container size, isn't your issue. :stoned::stoned::stoned::stoned: