Hi Nate-
I checked out your site, and I couldn’t tell which lightbox plugin you’re using (there are many out there), so I can’t say for sure what might be up with your lightboxes.
On this website, we use Responsive Lightbox and Gallery, which is pretty easy to use. It automatically replaces all your image thumbnails with lightbox links, and you can use a special code to make any link to an image appear in a lightbox, similar to this:
<a href="https://www.boldgrid.com/support/wp-content/uploads/2018/09/wordpress-image-designs.png rel="lightbox">Lightbox Image</a>
The important bit is at the end of the a tag, rel=”lightbox”. That will look like this:
Lightbox Image