[tudor]

Do you own the upstairs bathroom or does someone else? If you do, check what happens when you flush, if there is any leaking on the floor around the base of the toilet. If it's someone else, you could ask them about it, or ask the building management if there have been any repairs in that unit. A lot of bathroom paint problems are either leaks or condensation. Leaks are probably easier to deal with if you can repair them. It sounds like a small area for a leak but maybe it's a small leak. Good to get it at this stage if so. Big leaks can be dangerous if you have plaster walls and ceilings because they can collapse when they get wet.