I didn't go back and re-read, so I'm not sure what I said.

But normally, you'd want to manage metal removal by STARTING at low pH, with HEDP present, and then gradually allowing pH to move upwards as cal hypo is used.

The goal is to FIRST get the metal dissolved (Vit. C with no chlorine), SECOND to keep it dissolved (low pH + HEDP), and then THIRD to gradually remove it on the filter, while avoiding sudden changes in pH or FC that could re-stain the pool (gradually increasing pH & FC + cal hypo upstream of the filter).