Yeah, that coop is getting too small for 4 birds.
Probably also lacking in ventilation.
This.
And since they like to roost up high the top of the coop looks better to them than going inside.
You might want to look at this thread to see a good way to make your coop more practical: https://www.backyardchickens.com/threads/my-renovated-prefab-coop.1440258/