Page caches don't seem to expire

I'm having a major problem with Sitefinity 5.3. We have four web servers using the same Sitefinity database. When I log into Sitefinity and make a change to a page, that change isn't reflected on the other servers unless I recycle the application pools.

I set Output Caching to expire in 30 seconds, and I turned off sliding expiration. No difference. I can wait far longer than 30 seconds, with no traffic to the servers other than myself, and still, no difference.