Images disappeared from all posts and media library

I just discovered that all of the jpgs on one of our site Intrepid Travelogue are gone — captions and frames are there but no images.
There’s just the question mark. They’re also missing from the media library. They’re sized at 600 max. The gifs remain.
There are many, many posts here over a number of years. All was well at the time of my last post in December. Checked on it yesterday and most of them are NOT showing up.
It sounds like a glitch in one particular setting relating to all the jpgs, but I have no idea where to begin in trouble shooting.
Using Genesis 1.8.2 plug-in. Lifestyle Child theme.