Just bought a house with a pool. Concrete has blotchy brownish stains. Chemistry by Pinch-a-Penny is:

TC 5 ppm
FC 5 ppm
CC 0 ppm
pH 7.8
TA 75 ppm
CH 240 ppm
Stabilizer 80 ppm
TDS 500 ppm

Put 5 lbs of baking soda in per PaP recommendation. I ordered a Taylor 2600C kit but would like to get an idea of what these stains are since I have never had a pool before.

I have a picture but don't know how to imbed it.