Unfortunately this is not CSS related. The theme is altering how the wpautop filter is being applied so it is adding extra p tags where they shouldn’t. And this negatively affects every plugin, not just Connections, that put content on the page. It’s just really noticeable with Connections because of the amount of content it outputs.
Can I get a copy of the theme. I can take a look at the code to see what the theme author is doing?
Also, I see you’re using the LIZATOM SHORTCODES WORDPRESS PLUGIN. Looking at the CSS for that plugin it seems like it adds column shortcodes. The code many theme devs employ is from a tutorial. I wonder if this plugin uses the same code. I know you said you deactivated all plugins, but can you try deactivating this plugin again?