Are the stains natural on coated strings?

Hey! My first time using coated strings. Are those stains natural on a coated string? Other parts of the strings feel natural but those spots feel rough. Can it corrode in an unopened pack or will they wear of once I start playing?

Hey! My first time using coated strings. Are those stains natural on a coated string? Other parts of the strings feel natural but those spots feel rough. Can it corrode in an unopened pack or will they wear of once I start playing?