Poor Quality

Hi On the 1st of March 2024 i bought a 9ct Ring at Sterns, but I only started to wear the ring from the 6th of April 2024 because that’s the day I got married and a week later I started to notice a change on my Ring and it surprised me because I hardly wear it, I don’t wash dishes nor shower with it but it’s changing its original colour . 15 of April 2024 I then decided to go to the nearest Sterns( not the Sterns I purchased it ) to show them and the lady took it and she cleaned it, she couldn’t understand also because it’s written 9ct but it now looks bronze. After a day still it went back to the bronze. It hasn’t been 6 months or a year or A MONTH even but I’m not happy with the quality already