Ontogenie jewelry is 3D printed in wax and then cast in solid sterling silver, solid bronze, or solid brass plated with 14K gold. The sterling silver and bronze pieces will tarnish and discolor slightly over time. This is completely normal for these materials. Moisture, chlorine, sulfur (i.e. onions, garlic), hand sanitizers, and the oils in your skin may accelerate the tarnishing process. I recommend that you don't wear the jewelry in water, e.g., while bathing, showering or swimming. After wear, it's a good idea to polish the jewelry with a soft cloth and store it in a dark, dry place to slow the oxidation which causes tarnish.
If the jewelry should tarnish, it can be returned to its original brilliance and color by using a gentle, non-abrasive cream silver polish. I do not recommend silver wipes, baking soda or toothpaste as these can scratch the surface of mirror polished jewelry.
Highly detailed and textured pieces will be more difficult to polish because of surface variations. To polish these, I recommend using a very soft toothbrush with the cream silver polish to allow cleaning of small crevices. After polishing, you can remove excess polish by rinsing the jewelry in water and then washing the piece with a gentle detergent followed by a final water rinse.
The gold-plated materials, however, should not be vigorously polished as the plating is likely to wear off over time. The gold-plated materials are much less susceptible to tarnishing and will probably never need to be polished except with a soft cloth to remove fingerprints.
All of the jewelry should be protected from impact against hard surfaces as this can cause scratching.