Probably metal contracting or your clamp loosening after it cools off. Happens all the time. Tighten existing clamp, put on a new clamp, or a second clamp for inexpensive/simple starters.Why in the world is it doing it so long after the machine is parked?
I have a little coolant seepage on my ZD21 zero turn, I just discovered it's the drain petcock. Literally a drop or two between the weekly mowings. Just enough to be a pita....