I just got black suede slippers, I sealed them, then fell in some mud and tryed washing them, now they'r faded?

Okay so I got some black suede slippers, and I put suede and leather sealer on them, and it waterproofed them and everything, I fell in some mud the other day, and then tryed washing them, and the mud came off. But now there is a white line on one of them, and it won't come off, and what could I do to fill in the white spot? I was thinking black shoe polish, then letting it dry then seal it again, any suggestions? I would greatly appreciate it. :]