Changing justification on title and description

I set up a thumbnail gallery on my website at https://www.raptorresource.org/classroom/ (click the ‘about’ tab and scroll down to see it). The title is center-justified in the thumbnail. But when I click to open Lightbox, the title and description are right-justified. Any suggestions on where in CSS this could be changed? I tried changing right-justification in the one place I found it, to no effect. I also tested the gallery on a page instead of a responsive tab, and had the same problem.

Thanks!