No need to clear any caches. I'm sure it's just this, surprised you didn't notice until yesterday, this work has been going 24/7 all week. Definitely having a big effect on site performance. With a little luck, tomorrow will be the last day.
As I just posted here, the upgrade wrapped up a little ahead of schedule today. There are still a few things to do, but I don't expect them to impact site performance (unless there are problems). Enjoy the holiday weekend!