logInfo("Bathroom", "implicit " + previousState.toString)
The implicit state belongs to the rule, not the Item.
However I notice in your case it’s not going to work anyway. implicit previousState only exists for rules with changed triggers, and yours isn’t.
Which is the solution I missed of course … your rule runs on Item update, and Items can receive updates to the same value.
If you want your rule to run when the Item changes, trigger it from Item xx changed