Images not respecting cache headers?

My webpages update at 12am evrery day. My script will set a max age depending on the time to 12am.

When I check the request this seems to be working how I expect (in around 8 or so hours)
cache-control: max-age=29882, must-revalidate

However my images are not respecting the headers and they are showing a max-age of 30 days.
cache-control: max-age=2592000

After 12am the html is updating, however the old cached images are still showing.
How can I set the a maxage for the images or get them to respect the headers?

I know I can bypass the cache on the images that I want to update but there must be a better way?

3 posts were merged into an existing topic: Cache images to the same value as page cache-control: max-age