Listing blurry images | WordPress.org

Hi, 

I have installed the ESTATIK free plugin in theme Impreza en WP but the property list (used ES my_listing) shows with blurry front pictures. not sure why!??

Here is the page https://demo.mimarspain.com/en/inmobiliaria/

Thank you,

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