Uh-boy! You had a small problem and may have made it worse.
I home-brew and found out that chlorine bleach attacks stainless steel causing near permanent discoloration. The brown probably wasn't a "stain" it was probably rust. Lots of info on surface rust on stainless steel and how to remove it safely.
Sadly, I don't know a way to get the chlorine damage off without radically changing the surface of the material. You may eventually have to polish it, if you want the matte finish, you could have it lightly bead blasted (guessing). Maybe there is a smarter person than me here with a way. I'd like to know if there is.