Applications behind Cloudflare proxy subdomains are a lot slower

For the past few weeks we’ve received increasing reports that our multi-domain application is slower than usual.

After thorough investigations we noticed that the request is received and handled by the servers fast, but the browser developer tools is saying that the browser is waiting for response from the server.

Our setup is using DNS proxy to send to a load balancer which sends the requests to one of the servers of the application. When we deactivated the proxy on one of the domains, we noticed a significant improvement (from 54 seconds down to 4.5 seconds) while server load and performance was not any different than before deactivating the proxy.

Does anybody have any idea what might be the cause of this? I saw yesterday there were some problems reported for Cache module on, but there was nothing 1 week ago and nothing today.

I forgot to mention that sometimes even Cloudflare website is extremely slow like waiting for 30 or more seconds to load assets (js or css files)