Ok, let’s try this.
1. Flush the cache and deactivate your caching plugin
2. Go to “Appearance > GeneratePress” and deactivate the GP Premium add-ons one by one until the issue stops
This will tell us which add-on your server is having troubles with.
My guess is it’s the Blog add-on, possibly because of the image resizer. My guess is it’s server related since there’s thousands of other websites using it with no issues (for example: http://www.staceysrecipes.com – way more images as well).
However, if we can pinpoint it, we’ll be able to find a solution.
Let me know 🙂