Need suggestions on Odd Euro.|Skulls, Skeletons and European Mounts|Forum|Taxidermy Talk

I have a skull with antlers found on a gentlemans property that had been laying in the elements for approx. a year. He brought it to me to bleach and repair rodent chews. I have bleached it as I have always done BUT a part of the skull is now a mottled pink ! I have never see this before and I have done my fair share of Euro Mounts . I am guessing some sort of chemical reaction to who knows what ? Blood that has seeped into skull from decomposing in the woods for a year ? A result of soil stain since we live in an area that has red clay ? Im stumped !!! How can I correct this ? I certainly do not want this already brittle skull to fall apart ! Has anyone ever had this happen ? yes… a mottled pink ! Thank you for any help here.There was no flesh to speak of on it so I opted not to boil due to its condition but did soak in warm water to loosen dirt and grime adhered to it.