I had the same issue before. Magento compresses images sometimes—try adjusting the compression settings or using WebP. Faced this while working on mod the spike too, and optimizing formats helped a lot.
Thanks
Magento can use either GD or ImageMagick for image processing. ImageMagick is generally considered superior for image quality, especially for resizing and more complex operations.
You can check which adapter Magento is using and switch it (if ImageMagick is installed on your server) in Stores > Configuration > Advanced > Developer > Image Processing Settings. I was facing the same issue on bsd brawl and used these settings to solve it.