Very high server response time, websites stay stuck for ~10 seconds before loading

Hello, I had just moved to hestiacp yesterday, and today I noticed that my websites (wordpress) have high server resopnse time. The domains idle around for 5-10 seconds and then start loading.

I have checked cpu/ram/io/network usage, but everything seems normal.

Server is running on Debian 11 with default Hestia install (later i had disabled clamav i.e stopped and disabled its services and commented its mention in exim4 config) .

Is there anyway I can diagnose and fix this? I am lost.