The issue has been found and resolved. Although no changes were made by TDR, Google's Adsense decided to do an automatic revenue "experiment" on a percentage of visitors to see if it made more money. We've had auto-experiments turned off, it looks like they turned it back on. I've disabled it and these ads should disappear within an hour or so.
I'm not sure what's going on with the mobile top ad, since the Google experiment said it was only testing page anchor ads, but hopefully blocking experiments stops those too.