I'm helping out a friend with his pool, was planning on slamming tonight and helping him switch to BBB. The problem is light brown stains throughout his whole pool. CH was only 150 so I think this may have been the cause. I'm adding CH up as we speak.
Rubbing a tri-chlor tab
Rubbing Vit C tab
no fading with either of these
I did try with muratic acid at a 2-1 ratio and got a slight fade but not much.
15000 gall gunite with pebbletec plaster