Red tinted windows? Help!

I've spent hours building a house surrounded by a pool with a basement level covered in big windows. I did not have to use the bb.moveobjects cheat to place the windows there.

Everything was fine until I opened the lot just now to work on it and the glass of all the windows in the basement level have a red tint that won't go away. I tried changing the lighting, different windows, deleting and replacing them, restarting the game, nothing works. Yes, I have a lot of custom content in my game but I haven't added any new files since the last time I played and the windows were fine then.

Has anyone else had this problem? How do I fix it?