Masonry gallery image size

Hi, I have a gallery using the flexslider showing up on the masonry page and I like it, but I can’t get the image size correct. I fixed the problem of the gallery resizing by adding borders to all of my images so they are square, but they are cropping strangely, whereas I’d like them to show up completely. I looked at it with Firefox’s element inspector, and the problem seems to be that the “flex-active-slide” is set to 348px, but the images are set to “max-width:508” and I’m unable to figure out where they’re getting that number from. They seem to be auto-expanding to fit something larger than the actual window.
Thank you for any help.

The page I need help with: [log in to see the link]