In ground gunite pool done over last year, plaster, tiling and coping. Opened this yr to find long streaks, grayish color on white plaster. Company states it’s not from their work snd chemical company states they did their job right. Said it could be from metals, iron and other things in water. We had pool water delivered by two trucks. We had pool for thirty yrs and never had any streaks so don’t say it’s from our water. So ticked as it was such an expense and did everything we were told to do and still ended up with a problem. Don’t know where to go from here!
So those streaks first occurred when you opened for the 2024 season? If so, it's possible you are seeing some calcium staining, perhaps with organics trapped within. Typically we expect the cold winter water temps to counter-balance the pH that is rising, especially in a new pool (plaster) that is still curing over the winter. But perhaps the CSI level got too high?