Brown/rust staining on gunnite

We had high metal levels at the beginning of the season but fixed it with less-iron/iron-out. Since then our gunnite has turned brown/rust colored in many areas of the floor. Our chemical levels have been perfect for the past 2-3 weeks. We had this problem last year I believe and I've done enough reading/searching through this forum to make the link that this staining is due to the metals and I need to treat that to get rid of the stain. However, I am unclear on the specific process to do that. My memory is hazy from last year, but I think we had to drop the chlorine really low to treat the metal staining last year and we did it in the middle of summer so poof we had an onset of algae that we had to battle back for a few weeks. I am hoping to avoid that this year while still removing the stains. Anyone have a foolproof process for removing the metail stains while not causing an algae outbreak? TIA.