The brown may have turned to green because the high chlorine levels caused the metals in your water to drop out and stain your pool. You can tell if that's happened by lowering your pool just a bit and see if the walls appear yellowish. I would go to the metal stains forum and read everything you can there, especially anything posted by Marie (mbar, who is our resident expert on metals, second only to Ben!). She's got lots of first hand experience in metal control.

Janet