Image Teasers look bad in mobile

Hello,

I have placed the shortcode for Image Teasers on various pages on our site and when I view them on a a mobile device, they are not responding as they do on the Highend Demo. See attached before and after views. Is there something I’m missing in the code or something I can add to it to solve this problem? I like how they neatly stack in mobile view in the demo.

Thanks so much,
Amy