Hi Bula, your photos are awesome. I'm having this same problem: my landscape photos have their widths cropped on both the quick view and the product page. My site isn't live yet, so I can't share a link, but it's similar to all your portrait images.
Any help from the community would be greatly appreciated!
May 30: I figured out a possible solution. It works on my dev site for the quickview and details pages; I hope it works for you. I've added this into my Squarespace CSS editor:
/* quickview and details pages */
img {
font-size: 0px;
left: 0 !important;
top: 0px;
width: 100% !important;
height: auto !important;
position: relative;
display: block;
}