[Plugin: Jetpack by WordPress.com] Tiled Galleries not responsive

While doing some edits to my style sheet, I somehow affected the responsive quality of Jetpack’s Tiled Gallery. I’m not too sure where/how to find the solution. My website is: https://pjkelley.freeadepts.com/project/photography/

As I’m a graphic designer by trade, any help would be much appreciated. Thanks!