Unfocused images of the products on iPad and mobile

i have edited my photos using the mensurements and type of Photo used in Demo as a reference. In my computer they look good but both on the iPad and iPhone (tested in Chrome and Safari On both devices) i see the Images of my products on the homepage and on the specific page of each product very pixelated . As if using the smallest thumb of all generated in these devices. What can i do to solve it? Thank you.

The page I need help with: [log in to see the link]