It seems to have something to do with centering, as alchymyth suggested above. Here’s what I’m having to do: for every single post affected, I have to go into the HTML editor to delete the <center> tags, then switch over to the Visual editor to recenter the elements I just uncentered. I have to do this to a ton of posts.
It only happens to random posts, not all of the ones that have centered elements. Can anyone guess why this suddenly happened?
Also, I was able to fix the first paragraph of this post, but the rest can’t be corrected. Every single post in the same series looks the same.