Transparent png images suddenly have grey outline

Hello there,

Last night, without changing anything to my website, suddenly all transparent png images changed. They now have a grey transparent outline and I tried reuploading the same images with another name or any random transparent png and they all have that now.

On the other side, when I upload the same image as webp it shows as it should. No grey outline. But with PNGs, the problem exists.

I dont know what happened since I didn’t do anything. No new plugins, not changed any settings whatsoever.

Look how my homepage used to look and how it looks now with the grey outlines. Even the background of the home page (arrows) looks way different. It just seems awful.

MY HOMEPAGE: https://ibb.co/MSNV2zF

Do you have any idea what’s going on? I am so confused…

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