Stack gallery block on mobile (1 column)

Site URL: https://www.stickelsservice.com/about

Hey there! I'm having trouble finding a solution to the way my client's About page displays on mobile. They specifically wanted the founders on top (centered) followed by 3 rows of staff. Since they wanted it set up this way, I reworked it from a gallery section to a blank section with 4 gallery blocks and added this CSS to center it:

/* Center headshots */
body#collection-62265dff26fd182434bb01e6 .sqs-gallery-block-grid .sqs-gallery-design-grid {
    display: flex;
    justify-content: center;
      flex-wrap: wrap;
}

I can't for the life of me figure out how to get the headshots to stack on mobile into one column. See attachment for how it's displaying now. I was able to successfully stack the gallery section from the Services page: https://www.stickelsservice.com/services but not having any luck with the About page. Any ideas?