If you used starch it could be the starch that's is scorched. Take a white wash cloth and wet it and see if you can remove the scorch marks in one area. If it is starch, let the starch dry more before ironing and turn the heat down on your iron.

This is is one of the reasons that I don't use starch. I prefer a pressing spray such as Bounce (which has sadly been discontinued) or Mary Ellen's Best Press.