Featured Image blurry

Hi – I have downloaded and activated your plugin to automatically place a featured image on all posts. It also however places it on all of the pages too. When I look at the exact same image on the homepage slider it is crystal clear. However when I click into any page, the same image when used as a featured image via your plugin is blurry. It can’t be that it is not large enough as it is the same image I am using on the full-width slider on the main homepage. What can I do to make the featured image clear?

The page I need help with: [log in to see the link]