To ensure the longevity of your jewelry, I encourage you to remove jewelry when showering, swimming and while sleeping.
Jewelry will also tarnish faster when using different hair and body products such as gel, hairspray, makeup, lotion ect.
It is normal that Jewelry will tarnish over time, for sterling silver cleaning I recommend purchasing a silver polishing cloth from your local jewelry shop.
For Brass and Copper my suggestion for cleaning is to use a very fine steel wool and some dish soap, scrub until the brass or copper is back it its original color. Rinse and dry well.