I have a leaky 1st floor window in my house. The water (rain water) comes in through the 2nd floor window, infiltrates the wall, and streams into the 1st floor window area through the top window sill. The outside wall is clad in stucco, so the water is somehow getting in around the 2nd floor window (at the bottom of the window frame). I confirmed the leak by spraying water directly at the 2nd floor window, then watching it stream into the 1st floor inside window frame area. Any ideas what is causing it?