I have a plaster pool and have several stains primarily in the deep end and closer to edge of pool. The stains are about 1 to 2 inches in diameter and they are yellow green colour. They are also rough when you touch them and they feel like they are attached to the pool surface. I have tried scraping off but they are too hard.
I have a few trees close to pool and leaves always fall in.
My water is usually well balanced. I use a Taylors K2006 kit to test water and my numbers are CH=3.5 , PH=7.3 , TA=70, CA=600, CYA=20. I have an automated chlorinated and PH generally is around 7.4.
Any ideas on how to remove these stains.