Different size images

Hi,

I’ve just installed this plugin. I have a page set-up with one of my FB album. https://www.ooodlesofdoodles.com/Home/nursery/lulu-and-jaxon-current-litter/

For some reason, the pictures showing in the lightbox are not showing all in the same sized. Some are quite small. Yet on FB, they are pretty much all the same sizes. Is there anything that can be done to fix this? I have almost non-existent developer knowledge. Any help with be great. Thanks!

https://www.ads-software.com/plugins/tz-plus-gallery/