Both RC and IO have some issues with a slime or sludge when mixing it, which you can see when you go to clean the container, but the salt seems to be fine and it doesn't have an effect on corals or fish.
I also get the same brown film, have used it for years though and never had a problem in the tank.
I just switched to the Triton Method so will be migrating to Red Sea Regular Salt and I'm interested to see if the brown film remains (if I ever have to do another water change).