Does anyone know how to remove mould from bath mats? Mine's only 6 months old, and I guess it's because we always hang it over the bath the same side up, but scrubbing doesn't seem to clean it, and my bathroom cleaner says not to use it on porous surfaces, which I think rubber might be?? I don't want to replace the mat if I can help it, but equally don't want to accidentally bleach their little bottoms!!