Site and dashboard very slow, frequent 502 proxy errors

I have recently noticed that everything is very slow to load. The dashboard and site can take 5 to 10 seconds to load pages, and I’m frequently seeing various errors like 502 error and Proxy error.

The only thing I can remember doing is flushing the cache in wordpress.

Browsing any other pages on other sites, including a different wordpress login is fine. It seems specific to my login.

The page I need help with: [log in to see the link]