I'm running the latest version of WordPress and my theme (Hybrid News). At some point, (I'm not sure when it happened) older posts of mine started breaking their template. I use the plugins WP-Insert to show ads above and below content and Yet Another Related Posts Plugin to show related posts below content.
These plugins work great and I've been using them for years. I first noticed the problem about a month ago when looking at an older post. The ads inserted by WP-Insert and the links generated by YARPP are inserted within the <head></head> block and they are being rendered by the browser before the site title and the rest of the actual page. They are shown in the source code in both locations, so it's not just a CSS issue. They are also being inserted in the correct location.
This only happens on older posts. Since it is multiple plugins, I don't think it is the fault of the plugin. Since it isn't happening on new posts, I'm not sure it's the fault of the theme.
Any suggestions of where to look?