Yesterday, I left the water running in my 1995 AquaGlass jacuzzi-tub/shower unit on the second floor of my house. An hour or more later, after I had started a load of laundry (same floor, different room) water began pouring through the ceiling in the room below the jacuzzi. The tub was totally full, but did not overflow into the bathroom. So, where could the water have come from?
Water is like blood. A little goes a long way. Although you may have lost an imperceptible amount of water from the jacuzzi this would appear as a huge amount coming though your ceiling. I guess this first thing I would be doing if I were you is be calling a plumber to remove the sides of the jacuzzi for inspection.