Images have started to display too small

I revisited my site, built with a child of SMNTCS Retro [i changed some text colours] to update content a couple of weeks back and was disturbed to find all the images had shrunk to the size of tiny thumbnails. It’s strange because other wordpress sites where I use this same, elegant, theme, look fine. I haven’t fiddled with anything since the site was last looking as intended. I have tried replacing images and setting sizes as they should be but they still dsiplay very small. Any thoughts?

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