Blurry images on iphone

I just updated WordPress to the Version 5.6 and now SOME images are blurry when viewed on my clients iphone. Find on my Android.

I’ve isolated the issue to be caused by WordPress since it only occurred after updating WordPress on staging.

The issue was found on the following page:

https://tidgstaging.wpengine.com/achievements/

See comparison below:

iPhone: https://ibb.co/7bpM6XP

Samsung: https://ibb.co/2nHkLkz

Any idea why?

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