Thank you mbar, watermom, JimK and Ben for the helpful advice from experience. Please check to make sure my summary from all is accurate. Outside of bringing ph/chlorine levels up too high too fast, I did not add enough HEDP, and should not have used to trichor tabs ( in floatie and skimmer opposite of Culator)for chlorine source while using Culator. Stains have continued to darken while I am waiting on another batch of HEDP, Algeacide, and ascorbic acid, so, more questions: Are the skimmer tabs Ben refers to chlorine tabs or tabs for removing metals? The dosage on the KemTek HEDP for my pool is about 2 1/2 quarts per dose. I only ordered 2 doses, but sounds like I need more. How much should I be adding and how often - full dose each time I see stains after AA treatment? Should I buy sequestering test kit to take guesswork out like JimK? Once stabilized, what is the maintenance dose? By the way, how many quarts of HEDP are in a case?! Sounds like I am in same boat as JimK, and need a case or or two on hand for the near future. I also ordered a 4.5 Culator thinking the 1.0 was not enough - should I return it and continue with the 1.0? Not sure if it is working. Is still clean, but last time I cleaned basket, it seemed to have a clear gel on outside of the sack. Thanks for the help.