Golden Eagle Lite – White borders on feature items

Hello everyone,

I’m building and modifying my very first WordPress website. I’m using the Golden Eagle Lite theme, and I changed the background to ffffcc hex color. The problem is, there are white borders around the feature images that I can’t remove it.
I check the style.css, “contain” part but still can’t find out how to remove the border.
Do you guys have any ideas how to remove it?

My site is https://www.portlandgrind.com.

Please take a look and tell me how to figure it!!!