I just changed the theme of my Website, on WordPress/Woocommerce.
All pictures are blurry in laptops, both thumbnails and Single Product page.
When you click on the picture in Single Product Page, it becomes clear.
I have increased the product image size in tools.
I have regenerated all thumbnails.
You need to increase images size scale for catalog images in Appearance -> Customize -> WooCommerce -> Product images. To avoid blurry look for product images.