Plugin changes not applied to all posts

I’m revamping my blog, so I’m adding many new plugins, for things like adsense, related posts, social media sharing buttons, etc.

Changes that I make to plugins are not being applied to all previous posts, however. If I change the location of an ad, for example, some posts will show the old placement, some posts (generally, older posts) will show the new correct location, some posts will show no ad at all with the same plugin settings.

Refreshing the page and opening in a new browser does not fix the problem. Any idea what could be causing this seemingly random application of plugin settings?

edit: I deactivated the ad plugin, and ads are still appearing on my posts/pages. What gives? (This problem is not just with a specific ad plugin; it’s just what I’ve been working on currently. It’s been the same for other plugins.)