I Had A "chairside" Relining Of My Dentures A Couple

I had a "chairside" relining of my dentures a couple of years ago. A few months ago a piece of the lining appeared to be loose so I peeled it off. Denture still fits fine, but there's a brown stain on the site where the lining peeled off. My denture cleanser hasn't gotten rid of it as it does other stains. It doesn't show, but I'm concerned that there's some kind of bacteria or mold growing there. what do you think?