columns not responsive on smart-phone

I sincerely thank you for this wonderful gadget, because I have no idea what all the code this generates is doing under the hood, but it seems to work fine. I am using the “SiteOrigin Corp” theme right out of the box (ie: no child theme) – and expected the page-builder to do what you have done here. They should pay you a handsome royalty and build this into PageBuilder!

Take a look at the link above on a smart phone vs a desktop. Same three columns side-by-side on both. I’m pretty new at this responsive theme game (now that Google is forcing the issue) but my understanding is that on my phone the three columns should stack. They are squeezed together to the point that the are not functional for reading on the phone.

The shortcode I inserted:
[latest-selected-content limit=”3″ display=”title,content” titletag=”h3″ url=”yes” image=”medium_large” elements=”28″ default_height=”600px” default_padding=”3%” default_gap=”3%” tablet_height=”600px” tablet_padding=”3%” tablet_gap=”3%” mobile_height=”200px” mobile_padding=”3%” mobile_gap=”3%” css=”three-columns align-center ” type=”post” status=”publish” dtag=”yes” orderby=”dateD” show_extra=”exclude_previous_content,linebreak”]

I tried adding the coding below to the [Additional CSS] because I am using large images, and you suggested this to another user a couple of years ago and got no reply from him (her?)

.latest-post-selection article img {
height: auto;
}

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