I live in western Washington, a rainy part of the country. My home is 15 years old, conventional framing.
In several rooms of my house I have recessed lighting. The fixtures require that the insulation be kept back from the fixtures. Therefore, a square about 18" around the fixture is uninsulated. Directly below that uninsulated part of the attic the ceiling part is turning black.
In the attic I see no signs of moisture of other problems.