As mentioned above, silver will discolor. I touched base with my son who is a chemical engineer and deals with metals. However, on a side note, he did warn me about sweat from my hands which can act as an acid and cause discoloration and tarnish. I am assuming that you have a hand guard.
Tarnishield by 3M great product. I also use Hagerty's silversmiths' liquid polish which contains R-22 tarnish preventative. Non-abrasive and easy to use. Hagerty also has other products including a glove for cleaning.
Another excellent product is Allaro Deluxe polishing wipes. Great for touch ups each week to keep tarnish, dirt and fingerprints off all instruments. Also great on brass instruments. Available at: Band & Orchestra instruments and accessories with free shipping and low price guarantee from The Woodwind & Brasswind since 1978
Oh, also keep a silver instrument clean takes a lot of elbow grease...