AEM cloud, where to set image cache headers?

in our site, built with AEM cloud, all images have this header:

xx.jpg GET 200 www.oursite.com 57.8 kB private, max-age=600, immutable, max-age=300

There here are 3 issues:

1) max age should be 30 days, not 300 seconds

2) max-age is specified twice

3) we should really be using s-maxage in conjunction with max-age.

Where does one set this?  Do we have to use apache rules to overwrite headers in the cloud dispatcher?

What and where is the current 2x max-age set? It's not in our code or in any of the dispatcher or farms config that we can find.