Here is a quick tip to get your website at its peak speeds for loading and proper caching, this is something that I have fought with for a while.
As I use the Divi theme because of how user-freindly it is but with that said, it can hurt your website loading speed.
This has been the only thing to help me get and maintain proper website loading times and user experience.
Site Main Page:
Don't forget to check all of your pages, not just the main URL.
Here is example of another page on this site but all of them are Grade A except the main landing page which is the eye catcher.
I hope you find this helpful,