I think the vit-vape thing is a gimmick. One would have to vape a LOT of juice to get even the RDA of the vitamins. And vitamins are MEANT to be ingested internally, not by inhalation.
Plus, I think over time they will gum up an atty, as many are very large molecules, and most are high-heat sensitive and will decompose anyway. Vit-C is one of them. The OP mentions B12. Any idea of what cyanocobolamin looks like? Take a look:
Cyanocobalamin - Wikipedia, the free encyclopedia
I'm not inhaling the thermal products of decomposition of that!
As a chemist, I must say I find the vit-vape thing to be stupid at best, a con at worst, and without merit of any kind. You are far better off taking them as pill. And safer, both for you and your atty.