Images blurry on some pages

Hello,

When I view my Gallery page (giftedgalleryart.com/gallery) in the visual editor, its images seem fine (good quality, clear images). However, when I view the published version of the Gallery page, the images are extremely blurry.

The images I can see in the Media>Library thumbnails look blurry, but when I click to expand the images, the image looks clear.

I have added this code add_filter(‘jpeg_quality’, function($arg){return 100;}); to functions.php but it does not make a difference.

Does anyone know what else I can do to make the image quality better in my Gallery page?