There aren't any experts here, just folks, but we do have experiences. First, being vegan doesn't mean you're at all health conscious. Vegans are like everyone else, some do it in a balanced healthful way and some eat lousy food and do it just for ideological reasons. Being vegan is very hard to do in a healthful way because there's no complete protein and no B12, so you have to consider that. It's hard to do right. And here's the thing about antibiotics -- they giveth and they taketh away. The smell issue sounds more fungal than bacterial, but if antibiotics made it go away that does say something. But antibiotics also kill off a lot of what makes us healthy, especially in our digestive tract and in our immune system, and so they can almost guarantee something you don't want is going to come back in a worse way. That's why we aren't supposed to use them often. Fungal infections are especially prone to coming back because the antibiotics often don't kill off the eggs. Now, that being said, that isn't an area prone to fungal infections, and smell is usually associated with yeast. Is your tongue white? It could be thrush, though if it were your doctors should have been able to see it if they looked. The other possibility is that you got a placebo reaction from the antibiotic which would make it an emotional thing. Obviously, can't diagnose you but when you think something's wrong and docs don't find it, find better docs.
Have you ever had eczema? It's kind of on a continuum with allergies and similar. Maybe what you have is a form of that.