I had a lifetime of heartburn and it cleared up after vaping for a while, did you just quit smoking? I had a lot of strange symptoms at first while quitting, it was almost as if my body was trying to get me sick so I'd start smoking again, strange, but true.
If this isn't the case, perhaps it's the flavor of juice you are vaping or the nicotine content, I always keep a low nicotine vape around in case I overdo, I get a pepper taste in my mouth when I am dehydrated or have overdone the nic. I can continue vaping and not make it worse.