YouTube is owned by Google, and this mimics Google's own algorithm for establishing your site's rankings for search terms. You'll typically go through a roller coaster of ups and downs for a few weeks before the algorithm determines your new rank. In this case, YouTube is likely doing the same, looking to establish how much it wants to promote your videos!

Also note that depending on your audience, you could be seeing changes due to summer break, finals testing in college, and more. These next couple of weeks are the most turbulent according to one of our team members (@capnsostre) who's been running a YouTube channel for a few of years now.