smallpooldad,

You brought your PH down to 6.0? That is way too low to be suggesting anyone ever do in my opinion. I think you misunderstood Marie if you thought that was what she was suggesting or you meant to say 7.0. As far as I can recall, no one here has ever recommended anybody lower their PH below 7.0.
I've done the "ascorbic acid treatment" multiple times with great success. I have never lowered my PH below 7.2 prior to using since it will in itself lower PH. Erica (the original poster) does not have a metal stain after all. It is most likely leaf stains as John surmised or possibly algae. As Evan pointed out, her chlorine demand most likely stems from the Yellow out.

Erica,
You seam to be right on track now. I would suggest you only use Yellow out or these other products only as a LAST resort. Ben has stated in the past that "Using either Yellow-Out or Mustard Master will temporarily eliminate ALL free chlorine, replacing it with a chloramine, monochloramine. OTO will show a high chlorine level, DPD will show none at all" so it seams to me that if this wee to happen again, keep the "shock" levels up for a few days and brush to get rid of it. Also, heed my warnings and never let your PH dip below 7.0 in the future.

Dave