In all probability they are bleeding from the type of holder you are storing your chips in ... probably from pvc contamination ... and in most cases it will be the red color CHIPCO's that are most affected.

I've not seen similar effects of a CHIPCO bleeding in cardboard holders with mylar windows, or in the more brittle non-pvc plastic flips.

No, I make no claims to being an expert ... just relating to quite a few years of chip collecting unfortunate experiences.