I suggest you to switch on one or more of the following settings on the plugin’s settings page:
-Disable YARPP related.css stylesheet
-Disable YARPP widget.css stylesheet
-Disable WRI styles-wri-thumbnails_woocommerce.css stylesheet
In this general purpose plugin, we try to apply built in css stylesheets that is right for most sites and most themes. But of course in special cases there can be conflict between the built in css stylesheets of the plugin and your stylesheets of your theme. That is why these settings are made.
If you disable these stylesheets in the plugin using the settings above, your theme or custom css stylesheets are responsible for the appropriate formatting of related items, and you have the possibility to apply some more custom css that fit to your formatting needs.
I hope this information is help you to solve the formatting problem.
P.S. A similar (or same) question was answered here: