when the width of the website becomes less than a certain width (ie on mobile) you get a slightly different set of style rules kick in, which is adding a 17px padding to the top and bottom of the rows of your layout. So you'd need to add CSS to override that padding.
@media screen and (max-width: 767px) {
.sqs-layout .sqs-row .sqs-block:first-child,
.sqs-layout .sqs-row .sqs-block:last-child {
padding:0 !important;
}
}
this would probably resolve your issue. (It's a site wide change, so if you only want it to hit this section then put section[data-section-id="60e9829ec4c1a734c5d9c0cb"] before each of the .sqs-layout lines). this should remove the padding between the images, but leave the padding above and below the first and last pictures which is as it is in the desktop site.
if you wanted to remove those too, then add top and bottom padding inside your existing css for the sections content wrapper for data-section-id="60e9829ec4c1a734c5d9c0cb"
padding-top: 0px !important;
padding-bottom: 0px !important;
Hope that helps, let me know if it works
