A year ago I moved my marketplace website from http to https. I implemented some design changes at the same time, and saw a huge drop in traffic that we have not recovered from. I've been searching for reasons for the organic traffic decline and have noticed that the redirects from http to https URLs are 303 redirects. There's little information available about 303 redirects but most articles say they don't pass link juice. Is it worth changing them to 301 redirects now? Are there risks in making such a change a year later, and is it likely to have any benefits for rankings?