Images not working after 4.7.4 update

I’ve noticed that in the past few days, images are not showing up correctly on our site. They appear fine when I am building the post, but when I preview them, they appear as just a small square or not at all (captions still show up). Also, when I set the featured image, that appears as a broken icon in the side panel. But when I preview the post, it shows up correctly at the top of the post.

I thought that maybe this had to do with only previewing posts and when they published they would show up correctly. However, I edited an event today (https://blog.hcpd.com/event/ruralx-summit/) and the featured image for that showed up first as a broken image and then finally a small square when published. Also, posts that have already been published are not displaying images (https://blog.hcpd.com/2017/04/no-longer-business-as-usual/).

I am using Chrome but also noticed this problem when using IE.

All of my plugins are up to date and I re-installed 4.7.4 to see if that helps but to no avail. My website is: https://blog.hcpd.com.