I think it's because of the increased number of users on the site. Because of this, more questions are being asked and even more answers are being given. As such, musing is having a hard time upcoming all the work.

They have the option of reducing upvote power so that it gets to everyone but instead they're keeping it steady and upvoting as best they can.

With time, I believe their upvote power will increase and they will be able to accommodate everyone again.