I have a new pool with Aqua Blue Pebble Sheen. On the third day after filling a small brown stain appeared on a walk-out step in the deep end. It remained there for a few days and then just disappeared. Everything was fine for about three weeks and then it began appearing again, along with another stain on the same step and then a few down in the deep end (8ft) right where the floor rounds up to the wall. The deep stains (5 or 6) are spaced along a 15 foot area on the curve where the floor and wall meet.
Since the first stain disappeared my water balance has been great. I am VERY diligent on watching and maintaining the pool. I brushed twice a day for 3 weeks and the water has never been outside of these ranges.
FC: 2-3.5 Trichlor (Salt to begin in spring)
TC: 2-3.6 CC has never been >.12
PH: 7.2 to 7.7 Consistently at 7.5 (auto acid feeder) since before the stains appeared.
Alky: 84 - 101 The was consistently in the 80-90 range until last week to see if this helped the stains disappear
CH: 224 - 255 This has been rising slightly over the weeks
CYA: 28-43
iron: 0-0.1
Copper: .1
TDS 580-630
I use a ColorQ 7 Pro test kit and the pool store's LaMotte system.

The Pebble Tec guy and the pool store suggest using a metal sequestrant but it doesn't seem like I have enough metal to cause these stains...and the stains are not all over or on the walls. The Pebble Tec guy says if they don't go away with the sequestrant then they will send a quality person to look at it. He says this happens sometimes. The pool store sold my wife Metal Klear by Sea Klear...should I try this? I don't want to put unnecessary chemicals in the water. What else could it be?
Thanks, this forum has been great and has really made learning about pool care easy.
36,000 gln, Sta-Rite DE filter, VS pump, Auto Acid Feeder (Total Control) in South Eastern Pennsylvania