Antonio Melani Ballet Flats

Super cute, metallic silver and gray, Antonio Melani ballet flats. Only worn twice to get a pedicure and I wore the flip flops home. There is mark in the mesh material In the toe, its something brownish black. I have no idea what it is but it is hardly noticeable . (3rd and 4th photo). I have not tried to remove the spot, so it very well may be able to be removed. The spot on the inside is just residue from the sticker where I tried to remove it. The bottoms still look new!