The reasons are on the wall. Hook-Bang broke the buddy system, Sheep Nun didn't use an umbrella, and Half-Bang and Protagonist are oversleeping.
These are the senseless reasons I am talking about. Especially the umbrella. I think Star's punishments are normally targeted at making them better people. But here, Sheep Nun went to seek her friend, Half-Bang and Protagonist basically haven't slept all night in order to make that wooden sheep figurine. Hook-Bang was heartbroken and wanted to do something good for Sheep. And Star's spy birds have seen it all. What's going on...