Why are the Images being delivered 3 times.

Hi.
Some of this is down to the "server" you are calling the asset from.
When you have a different host, even if the same file, generally browsers will not see it as a match and so not pull it from cache.
Cache in most browsers is handled as site (URL up to first /) and then the file name.
So, this is why when the host and file match, even with parameters after the file name, you see one is from cache.

This is actually good behavior as if my website had the same file name for an image you wouldn't want to show my image but the one from your site.

If you want to ensure that all images are cached you probably want to put a custom domain (same as website) on the API gateway.