Why do my edited images appear pixelated on my website?

Hello. I am using the Taste theme. When I edit an image before using it on the website it loses a lot of quality. It seems to whether I am using Canva Pro or the Pro version of Adobe Express. If you go to the bottom of my website gallery page, you can see what i am talking about. The 1st image is unedited, the 2nd was resized on Canva the 3rd on adobe. They all started out as the same picture. Thanks for any help!

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