Can eliquid ferment in a tank?

[xxxSapphir3xxx]

I've been vaping some of the same flavors for awhile, and 1 of them, a blueberry cream that I added sweetener to now smells fermented. Is this possible? It doesn't taste off, but it smells like pure liquor only in the tank, not the bottle. I even cleaned out the tank, charged the coil, smelled the juice out of the bottle and it happened again with fresh juice, fresh coil and a cleaned tank. The juice was made on 9/5/14 so it's not old and again, it doesn't smell like it's fermented in the bottle. I also smelled the sweeter and it has no smell at all, also mfg date of 9/5/14.