Help removing stain

[macdonkk]

Hi everyone, just opened my pool a few days ago, and I noticed a lot of staining on the floor, sides, and steps of the pool. It was resurfaced with diamond brite last July, and was fine at closing. I scrubbed with a brush, vacuumed, etc and nothing could get the stain out. Just tested the water and

hardness - 500
Total chlorine - 3
Free chlorine- 1
PH- 7.2
Alkalinity - 120

I’ll add a few pictures to see what you guys think it is. Iron or copper was my best guess. Any advice on it and how to get rid of it are appreciated. Thanks for your help! - Keith

 

[macdonkk]

17k gal, gunite (Diamond Brite), Hayward 1.85 THP VS pump, Hayward Goldline SWG, STA-RITE system 3 modular media filter, Taylor testing kit