Several months ago I've bottled three gallons of blueberry wine. This morning I've noticed one of the corks popped off. Several months before bottling I've added potassium sorbate, f-PAC, etc. I thought for sure it wouldn't ferment anymore. I find it strange that it took this long to pop a cork. Is this because I didn't degass it? Now I'm concern about my other bottles from the same batch.