Recently we've noticed a straight line of brown spots appear over our dinning room. The area above those spots is a hallway, next to the stairs and there are no vents of any kind. It is also a good 15-20 feet away from an outside wall. We are a middle unit in a town house complex so only two outside walls. Could this be a drainage problem from a shower drain which is about 10 feet away? I haven't noticed which way the shower drains to go down to the 1st floor so not sure if this is part of it's path or not. Could this be some other problem not related to the shower? The house is about 7 years old so relatively new. Thanks for your help.