Pictures Displaying Oddly in Grid

I’m loving the plug-in, it solves a huge problem for us, but there’s one odd thing. As per question elsewhere, I’ve changed code so that the captions show without hover or click (which is awesome!) but for some reason on tablets and pcs, the images are tiling oddly, sometimes I get the assigned 4 pics in a row, sometimes only 1, sometimes 2. On a phone, everything looks perfect. Any ideas why?
You can see the page in question here:
https://www.lacenterschools.org/elementary-school-staff/

Thank you again for your excellent plug-in!