Is this normal toning?

I’ve only had this coin in my case for a couple of months, and it went from this: 

To this:

Similar things are happening to all of my silver coins but not this fast.

Is that like a white residue that you can see? I don‘t want to assume as the lighting and angles of the images are different.

If it is (and I’m not saying this is the cause or you use such products), but it reminds me of how silver Polish goes (or similar products designed to leave a finish on top of metal) when it starts drying out. 
 

Just a thought if you have bought recently, maybe someone used something to get a more pleasurable finish on the coins.

It’s the gray stuff. It has been appearing in weird patches. some places are grey, others are still shiny  like when I bought it. The guess that someone polished it before selling is probably the best guess.

Pop it in some acetone for a few minutes then rinse thoroughly, hopefully that should get rid of whatever mystery substance is on there.