I have a newly plastered pool (about 2 months now) and there's a brown line running from the equalizer, anti-vortex grill on the pool wall to the bottom of the pool. There's no other stains in the pool, and the water chemistry is perfect. I haven't put anything like shock in the pool, and the skimmers are all new and were put in by the same pool company that did the plaster.
I tried scrubbing it with a nylon brush, and then a steel brush, but it's still there. It's not horrible, it's a light brown line, almost like light dust trail, but it's still concerning.
Any idea what's going on?