When the tile setter I hired to do my new home did the shower, he cut the end pieces with a tool that scratched the tiles about ½” from the edge. This was not noticeable until my ex-wife started using a black rubber squeegee to clear the water from the walls of the shower. At the time, my vision wasn’t good enough to see any change. After getting cataract surgery, the black in the scratches is very noticeable. I’ve removed most of the black with WD40, alcohol, whitening toothpaste and baking soda, yet some still remains. What do you recommend to remove the black from these scratches and edge cuts?