Stretched Thumbnail Images

Hi,

Thumbnail images in the plugin are all stretched. Using WP 3.8.3 and the Sahifa theme.

Not currently using the plugin because of this but thumbnails are displaying OK with another popular posts plugin – but I’d really like to be able to use the tabs.

http://www.selfpublishingreview.com/

https://wordpress.org/plugins/popular-posts-tab-widget-for-jetpack/