Blurry product images and thumbnails

Hi, i am having a few issues with my site https://www.shortstuffseeds.com

As you can see on the product page the images are blurry:
https://shortstuffseeds.com/shortstuff-seedbank/

but when you click on the images and see the full sized ones 800px x 800px they are crystal clear.

Also, on this product https://shortstuffseeds.com/shortstuff-seedbank/auto-purple-amnesia/ the gallery images are fairly clear but for this product https://shortstuffseeds.com/shortstuff-seedbank/333/ they are horribly blurred.

Am i doing something wrong when uploaded the images?

Any help will be gratefully received!