Evan, since I think the same thing just happened to me to with "pool store salt", I just added some sequestrant right away. I didn't mess with the PH 'cause I'm not brave enough for that stuff yet. I did brush the stains every day and one day they seemed to be gone. I think the trick is to do something right away before it gets set in "stone".

Now, I'll be extra vigilant when adding salt or new water and make sure I have sequestrant handy. Yeeesh...it seems strange to have to sequester a pool instead of a jury.