Recirc line
A recirc leak often follows the clock, not the weather.
Buildings that keep hot water at the tap use a return line. That line stays warm. A leak on it can stain ceilings far from any shower that was running.
Ask whether the building keeps hot water ready at the tap.
If yes, recirc piping is in play even at 3 a.m. with no one showering.
Warm wet drywall on a return run is a clue.
Thermal patterns on a recirc line need context. Heat does not equal a leak by itself.
Do not shut the recirc pump as a hobby.
Pump changes affect every suite. That is a building-operator decision after the leak is understood.
Questions people ask
Can a recirc leak be a pinhole?
Yes. Recurring holes on the hot return belong in the same log as other domestic pinholes.
Will stopping the pump stop the leak?
It may reduce flow. It does not repair the hole and it may create no-hot-water complaints.