my site was working fine till a few months ago thanks to "jch plugin" and "cache plugin" and page load time improved to 3 seconds and response time under 1 second.
but suddenly response time went up to 7 seconds.
when i turned back a backup from 8 month ago, the page loads in 3 seconds. so i guess the problem isn't from the server. i updated everything in the old backup and still page load time was 3 second. so i guess the problem isn't coming from updated extensions and Joomla (I GUESS)
i turned on "joomla debug" and i didn't see anything wrong in it. maybe i didn't check it right.
what are the ways that can help me find out why TimeToFirstByte is high? what can i do to find the problem?
is there any plugin or something that shows what happens in ttfb time?
any help would be appreciated.