The answer to 'skylight water stains' is that they are typically caused by leaks around the skylight. Common symptoms include water stains on the ceiling or walls around the skylight, and visible cracks or gaps in the skylight frame. Solutions can range from simple DIY caulking and sealant repairs to more complex issues that require professional roof replacement or skylight installation.
If the stains are minor and you can easily access the skylight, you may be able to fix the problem yourself by applying a high-quality silicone caulk or sealant around the edges of the skylight. However, if the leaks are more significant or the skylight is difficult to access, it's best to call in a professional roofing contractor to properly diagnose and repair the issue.