It's usually oxygen that oxidizes things seeking its long lost lover, the free radical...chemicals can act as a catalyst or create all-new ugly chemical reactions with vulcanite. Regardless, it can be a problem.
Are you using sopping wet pipe cleaners with your alcohol of choice? Scale back on that a little, I use barely moist cleaners myself. Also, being an outside smoker, I use unscented/unflavored chapstick with sun protection factor (SPF) that, when applied thinly to the vulcanite stem, not only helps protect against the UV exposure damage, it gives a slight added protection to the stem when cleaning.