Puzzling. My water test doesn't show any metals, including iron.

I'm now second guessing my iron deposits diagnosis, but my stains didn't seem to respond to high chlorine levels, and did seem to respond to 1 Qt Metal Out.

I decided to continue treating these stains as though they were iron deposits.

Yesterday's water test results are as follows:
FC 4.9 ppm
TC 4.9 ppm
CC 0 ppm
pH 7.8
Hardness 170 ppm
Alkalinity 140 ppm
Cyanuric Acid 30 ppm
Copper 0.0 ppm
Iron 0.0 ppm

My FC this AM was 2.0. This afternoon, it will be approaching zero, and I'll add the Stain Out, per the label directions. I'll repost.

Given the water test indicated no iron, the lingering question in my mind is that these stains could be tannins from the oak tree leaves, but I can't explain the lack of response from my high chlorine treatments.