Oura seemingly tarnished the silver ring I wear on the finger next to it…?

Ive been wearing my new silver Oura 4 on my right middle finger for one week today. I also wear a 925 silver band on my ring finger next to it, this one for 10 years now. This morning, I noticed my silver band turned dark… bronze…purple..? Tarnished silver...? I can’t figure out why and no combination of words I type into Google is helping. Has anyone had this experience? Could it be something with the metals interacting? The silver Oura is totally fine and perfect. Side note that may be irrelevant but: I noticed the drastic change in color right after I was finished brushing my teeth with my sonic toothbrush… could this be related??? Idk. I see people clean metal objects/jewelry with sonic technology so maybe that caused the change…?