Custom CSS Issue

I’m using some custom css to style the plugin, including a bottom-border between each review when using the full width display option. I’m also using the last-of-type selector to avoid having a bottom border after the final review on the page.

The issue is that the plugin seems to view each third review as a last-of-type, and therefore omits the border after the 3rd, 6th, 9th etc. reviews.

I’ve also tried first-of-type, but the same thing happens. Both WP and the plugin are up to date and the issue occurs in all browsers.

Thanks