Hey Cole,
I think the site looks great and is very useful. The one suggestion I have would be to add a bit of space to everything to give it some breathing room.
These are the changes I made: try them out and see what you think.
body { padding: 10px; background: #f0f0f0; }
#groups { grid-template-columns: repeat(auto-fill, minmax(350px, 1fr)); }
.group { padding: 10px; margin: 4px; }
.group > span { margin: 0 20px 20px 0; }
.gmatch { padding: 6px 0; }