I’ve always thought that Sirius would be able to tell when Remus has bad mental health days because he stops cleaning up. He gets messy along with his area of the dormitory. When Sirius notices, he has a habit of keeping Moony’s space clean for him, just because he knows it helps him feel better. I like to imagine Remus just waking up from a depression nap with Sirius sitting there with tea for him folding his laundry and putting it away neatly – something he doesn’t even do for his own clothes.