Image spacing on mobile

Site URL: https://www.timdenton.info/

I'm having trouble with my images spacing correctly on mobile. I'm happy with the desktop layout, but the single images have a larger gap on them on the mobile view. I've tried many things but just can't get this gap to reduce in size. The gap between all the images that are two side by side on the desktop version space out just fine, its just the single ones. Hope that makes some sense. 

Any help much appreciated!

#collection-5e98a790f7394c3f871bd010{
  @media screen and (max-width: 640px) {
    .sqs-block image-block{
      padding-bottom: 0px !important;
    }
  }
}

Add this to the Custom CSS