I have just bought a new silver trumpet. When I bought it, it was flawless. All shiny and brand new. I've been told my the cashier that I should try to just wipe it with a towel after I play to get the finger prints off. I've been consistently doing it for about a month a half. About 2 days ago It was really late and I had to get to bed so I just thought one time of not polishing wont hurt it. The next couple days of practice, I noticed it started to form brownish-yellowish tarnish ugly spots. One big one is on the first valve. Right next to the thumb slide. The ugly spot doesn't seem to be a finger print, but it seems to be the underside of my finger. There's another spot just like it. That cashier also said if it gets tarnish get a towel, put some toothpaste on it, and wipe it. It will come off. Needless to say that did not work. Any advice?