Will your charms tarnish?
Eventually, yes. Sterling silver has copper in it for strength. Fine silver is 99% silver but it is too soft to make jewelry out of unless there is a plating like rhodium to make it strong enough for use. The copper content in the sterling will cause it to tarnish. It will also corrode if exposed to chemicals such as chlorine, acids and salt. This includes sweat. Tarnish can be removed with a treated polishing cloth while corrosion is permanent.
Where should or shouldn’t I wear my sterling?
Sterling shouldn’t be worn in the pool or the ocean. While light sweating won’t hurt sterling, exercise level sweating will corrode sterling. Avoid wearing it while using cleaning agents such as chlorine or anything else corrosive. If you get something like these on your sterling, wash it in soap and water right away. Even though sterling doesn’t do well with anything corrosive, your normal body oils are great for it! It’s fine to wear in the shower and to wash with soap and water. When you do this, your sterling should not tarnish but develop a nice, warm patina over time.