Wet & Forget Indoor will clean up mold and mildew as well as disinfect and deodorize your interior surfaces. What you may be seeing on the surface is leftover staining from the mold or mildew. Wet & Forget Indoor isn't designed as a stain remover, however, you can give the surface a quick wipe down with a cloth or sponge 10 minutes after applying to help pick up some of the staining on smooth surfaces. We'd like to help you further and learn more about your application, if you could please give us a call at 888-727-8524.