Dishwasher operates well. No leaks. Dishes on top rack get black spots on them when unit is run. So far we have tried running vinegar through wash cycle with dishes, changing to cascade dishwasher detergent, IRON OUT has been run through cycle with no dishes. Maintenance person has put a towel over bottom inside of dishwasher to see how many spots turn up when unit is run - only a few when no dishes were in dishwasher n-.
Does anyone have any idea what the problem may be?