It would be difficult for the rebar to rust that quickly. That's more than likely a stain from the dirt where water is leaching through the shell.
Try cleaning it with some dish soap and a brush and see if it clears up
Thank you. I will give that a try and report back.
Yes, if that is rust it will come through the plaster coat if left as is. They need to chisel into the gunite, cut out the offending rebar and patch it prior to plastering.
Perfectly normal
What do the plans/ engineering specify?