Display 3 images per row in gallery block on mobile but for only one page. Also 3/row only one gallery block on a page with multiple gallery blocks

I'm looking for two solutions for customizing gallery blocks on mobile only.

1. I would like to know how to change a gallery block on only one page of my site to 3 images per row. I've tried code I've seen on other forums but it seems to change all gallery blocks on my site. This is the specific page I'm looking to change to 3 images per row on mobile: http://www.pink-creative.com/randomcoolstuff

2. I'm wondering if it is possible to customize only one gallery block on a page with multiple gallery blocks. This is the page in question: http://www.pink-creative.com/goodnews and the specific block I'm looking to customize to 3 images per row, while the other blocks remain as they are, is http://www.pink-creative.com/goodnews#social 

Try this code

@media only screen and (max-width: 640px)
{
  #block-yui_3_17_2_1_1697227978381_390812 .sqs-gallery-design-grid-slide, #block-yui_3_17_2_1_1697141864237_189679 .sqs-gallery-design-grid-slide{
    width: 33.33% !important;
    clear: none !important;
  }
}