Fixing low quality Wix gallery images

My brother has a website ( https://spencerbeals.com , go buy some art!) which uses Wix. There's a product page view where you can see multiple images of a given piece and click to zoom in, but the gallery images are somehow lower resolution than the non-zoomed version, making for a pretty bad user experience. I couldn't find anyway to change this in the tool (or even any forums with people asking…