Why does some store bought kimchi ferment faster?

Hi all,
A month ago I bought several packets of kimchi from my local korean shop. I have two left, unopened, in the fridge. One is fine, and the other has bloated. I know that the fermentation process doesn’t completely stop in the fridge, but I thought it was normally slow enough that the gas absorber in the packet could cope… So my question is: Why is one packet fermenting faster than the other?
I’m probably a ninny, but I’m worried that something might have gone wrong with the bloated packet, some lapse in sterility or miniscule damage to the seal to explain it.
Can anyone set my mind at ease to why one packet is producing more gas than the other, when they’re both in the same fridge? Thankd