OK, I have some GN mats with the letters on them. It seems that the letters are some kind of white embroidery. I tried claening the letters and it just got really worse really fast. I tried a carpet cleaner, dishwashing liquid and then detergent. Now they are greyish. What would be the best thing to do. I painted them with a white Sharpie piant marker and they got OK after like 3 times (too much time). I was thinking of white nail polish. What do you guys think?