There is some stuff you need to consider. For me I work also for Jewelry brand, Well known one, We don't sell online but I can Help you Because worked with others before. Simple you need to consider some analytical stuff first. Such as the "Bounce rate, Session duration"? 2nd you need to check user experience. have you tried doing demo Purchase to check if everything works properly or not? 3-Conversion code is well installed? 4th Have you tried social media? 5th tried Social media store? 6th, Have you done competitors checklist? "Prices, Ads, Marketing strategy, Marketing targeted, Etc. " 7-PLease check your keywords and the old campaigns and analyze them, Might be something changed recently caused that poor performance.