You will probably have to do a stain treatment. You are using a product that is probably a sequestering agent - it will bind with the metals that are suspended in the water, but if the stains are embedded, they will not lift off with just the sequesterant. You can get ascorbic acid which is vitamin C, or there are other products that use oxcylic acid? I am not sure if that is the right spelling. I always use the ascorbic as it is the most mild. Here is a link to buying it cheaper than the regular pool products.

http://www.msm-msm.com/store/agora.c...scorbic%20Acid

http://www.chemistrystore.com/Ascorbic_Acid.htm

If you chose to do this treatment, I can give you directions on how to use it.