Nobody takes a bath while in uniform or de-evolves into earlier life forms.
Okay, let’s put everything, direct clues and non direct clues together:
Clue 1: We’ve never seen that room before.
Clue 2: That’s a new one for the cleanup crew.
Clue 3: Worf gets to blast something new.
Clue 4: Really? Did it really have to blow up?
Clue 5: You have to wonder, did he still have this habit on DS9?
Indirect clues:
Neither the Crystaline entity nor Q appear in this episode.
Picard and Riker have similar conversations in this episode and "Contagion."
No asteroids were phasered, torpedoed or otherwise destroyed in the episode.
A strange phenomena is at work in this episode, but not the quantum filament from "Disaster."
Clue 6: So Guinan tells him one thing, very clearly, then he goes and does the exact opposite?