We have a condo on the 3rd floor with one more unit above us. Our tenant just informed us that there are stains running down the middle of the ceiling throughout the whole condo. Some stains near the vents on the ceiling as well. Plumber/handyman thinks it is the HVAC unit running down the middle of the units ceiling that is leaking at each of the 10ft duct. Condensation dripping at each of the seals. Please help. Need to know if anyone else has experienced something like this. Also who is responsible if this is the case?