I macerated my bear skull and it looks like I got rust stains on a few different places on the skull. However, I used a plastic five gallon bucket to let the skull sit in with heated water. Has anyone else experienced this? It looks like rust stains but I don't think it could be Iron because no metal was around. I degreased the skull in acetone and whitened with 9% Hydrogen peroxide. Not sure how to remove stains?