I have a SRD strop that has always been hanging in my closet. Every now and then I will rub it down with my hand but not often. I have noticed for about a month now it will sometimes leave like brown smudges on the razor that look sort of like water stain with brown spot here and there. The marks come right out if I rub it once with a white t shirt. Only thing I have done to it is use 2k sand paper on bottom left edge to sand out a nick that I just gave a good rub after that (did this way before smudge problem).

has anyone had this happen before and know what I should do to fix it? Not sure if smudges would cause problem to razor if I don't rub them off.