Regenerate Thumbnails completely pixelated all of my images

What am I doing wrong? I ran the plugin and it converted almost all of my images but now almost all of my images are ruined and completely pixelated.

You can see the updated photos on my website here: https://www.windahla.com

Before some of my photos we not being compressed correctly and coming out pixelated in the thumbnail section so I downloaded this plugin and ran it but this has just made everything much worse.

Any help would be much appreciated.

Best,

https://www.ads-software.com/plugins/regenerate-thumbnails/