sirfpsycho Thanks bro I did it ($host or example.com both) and it's working fine now.
I set Cloudflare full SSL (cert and Pvt key) to my server A and I got 523 error. then I set Cloudflare full SSL to server B also and then it's working. if I disable SSL from server A then I got a 502 error and when I disable it from server B then I got a 521 error. Both enable and it's working. So is this ok for SSL to set both servers?