Performance issues – Pages under /index.php/

Hello

Let me start this off by saying I have no formal HTML or CSS training and and am going by trial and error. I have also searched through other performance issues logged and cannot find anything describing what I am experiencing.

I have managed to reduce my home page load time from 12-20 seconds down to 5.5 to 8 seconds.

Any pages where the URL refers to under /index.php/ take an average of 11+ seconds to load.

I have W3 total cach running as well as did some content changes based on feedback from gtmetrix.com and tools.pingdom.com.

No matter how much lack of content the page has, the wait time on the page coming back is incredibly slow. From monitoring in debug I can see no issues with the speed the JS and CSS are running, it seems to be all initial page requests are taking a while.

Basically it feels like whenever a page is under /index.php/ the server is taking a while to find it.

Main site:
https://sector17.co.za/

Example of Slow pages:
https://sector17.co.za/index.php/members/
https://sector17.co.za/index.php/updates/
https://sector17.co.za/index.php/calendar/

When I monitor in debug and on various testing sights and look at the waterfall, the first request is always what takes an average of 5+ seconds.

What I need to know:

If this is because of an indexing configuration on the website itself, where to look would be greatly appreciated.
If it is related to response from the host, I need this confirmed so I can address it with host.
Thanks to all who respond!