Mixing argentium with sterling silver pieces

I have recently been using Argentium for my Jewelry pieces.

Just before Valentines Day I made some heart pendants out of 925
Sterling Silver. I used my Argentium for the jump rings. Within a
couple of weeks my heart pendants started getting a coppery tinge
starting where the jump ring is and spreading throughout the piece.

I tumbled with steel shot and Rio Grande’s solution. The coppery
color doesn’t resemble regular tarnish and happened so quickly, I am
wondering if the combination has caused this or if I am doing
something else to cause this.

Has this happened to anyone else, or does anyone know what could
have happened? It cleans off with easily with a polishing cloth.

Thank you