Some images presenting as low-res in Bridge slideshow, but not all

I've put together a folder of images to send, and like to do a Bridge slideshow to see how they'll appear. Most images look very sharp, just as they appear when I open them in their apps or Preview. But a few present as really soft, even though they were processed to the same specs. These same images look fine when viewed outside of Bridge.

I'd love to know what's causing this, but more importantly, I am concerned that the folks I'm sending this to will view it with Bridge and have the same issue. I've never had this problem before. I'm using old CS6. Thanks.