We are attempting to resolve a similar problem with our as yet to be swam in pool. The finish was stained very dark streaks of blue or black as the pool was filling for the first time. It has soaked for 80 or so hours in acid treatment and has now been drained to treat the spots more closely ?? I am being told that it happened because of something in my well water. I was also told that our pool company has recently experienced several other similar problems with recently completed pools.. Any comments or suggestions would be greatly appreciated.