WP Downsizing Featured Images

I took over my company’s WP blog and cant seem to figure out whats going on with the featured images. When I add a featured image to a post like the one in the link, it is automatically downsized to 670x300px, typically resulting in a blurry image. I tried adjusting the image size settings in Settings > Media, but no luck. The featured images that I have been uploading to the media library are typically 1340×600. The image size is only converted to 670×300 in the post – not in the media library which still shows them as 1340×600. Theme is Formation Pro. Any ideas on how to resolve this?

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