I wonder if this is related to the massive increase (quadrupling) in DNS traffic just to my own domains as of January 2020 that has become the new normal ever since. Figure 2 in the article lines up with mine exactly: https://i.imgur.com/5yuQ6rY.png
Mildly annoying because I was only paying my DNS host for 1 million queries-per-month and had to increase my plan. I only get aggregate statistics so I am unable investigate blame.