Images with rounded corners–how to get rid of that?

I put together the site at http://mttanzania.com/ with Enfold. The client loves it but pointed out today that one of the front page images has rounded corners, while the others are all square. He’d like them all square. I can’t see how that image (over the Services button) is getting the rounded corners. The original image in the media library doesn’t have rounded corners, and the first image (over the Machines button) has square corners. It’s not a styling issue, as both images have ‘default’ selected for styling.

How do I get rid of the rounded corners on the Services image?

Thanks,
JC