Materials like silver and gold will naturally oxidize and change to a variety of beutiful shades. If you want your pieces to remain bright you should clean them often with a polishing cloth.
Dust, cleaning products, water and direct sun light can also alter the appearance of the jewels and speed up their oxidation. To prevent silver from tarnishing and to slow down the peeling off of gold plating and oxidation, do not wear jewelry while showeing, bathing and exercising. Take the time to store the jewels in a sealed bag.
You are always wellcome to send them here for a professional cleaning or gold plating / oxidation renewal.
Information regarding online dispute resolution pursuant to Art. 14 Para. 1 of the ODR (Online Dispute Resolution Regulation):
The European Commission gives consumers the opportunity to resolve online disputes pursuant to Art. 14 Para. 1 of the ODR on one of their platforms. The platform (http://ec.europa.eu/consumers/odr) serves as a site where consumers can try to reach out-of-court settlements of disputes arising from online purchases and contracts for services.