Images are sharp in editor, but not when published

So i have a bit of a weird problem. when I upload photos to my wordpress page, they look sharp and fantastic in the editor. but when I view the post in preview mode or actually publish it, the quality goes down the toilet.

here’s an example (the image at the TOP is from editor, the image below is how it appears when published). Note that there is discoloration and pixelation around the the side table for this airline seat, and around headrest of the seat.

https://prntscr.com/l9pt3j

any ideas what’s going on? I’ve already edited my JPEG compression with the following line in my functions.php file:

add_filter(‘jpeg_quality’, function($arg){return 100;});

but no luck.

The blog I need help with is milelion.com.