All in a row...

[Scott Griffith]

My #3 hive is doing something I have not seen and I don't think I have read about. They are forming a single and sometimes double line above the entrance. The line is about half the width of the hive. The are facing the entrance (down) and seem to move down and up in unison. What is this behavior?

[The Honey House]

This behavior is called wash boarding.
(Note: I have observed this on "happy hives", so I'd say that your hive is probably doing fine.)