Reservoir for radiater loses water/antifreeze supply… No wetness around tank, no wetness on hoses. Can see drops under car (not water condensation from air conditioner) more looking like antifreese. If we turn air off leak stops.
Are your radiator fans coming on?
If they aren’t that is the problem.
Unlikely, but possible, the cap on the reservoir is bad.
If your car has a cap directly on the radiator, I suggest you check the coolant level there in addition to the reservoir.
The engine is leaking coolant, your mechanic will need the lift the vehicle and inspect for leaks.
This is done only with the engine completely cold, to be clear.