You are pretty much 100% correct, amphiprion. The issues that took place with the kent salt coincided with the move to the ESU/Coralife maufacturing plant. When the Kent salt was being made by ASI, they provided their own trace element and vitamin mixture which was added to the IO basic formula in lieu of the IO trace elemnt and vitamin mix. It really was a very similar salt. Also, your comment about Aquarium Systems is somewhat false. This was well after Marineland purchased Aquarium Systems, but the company does still exist today. I live 10 minutes from there and see it all the time, right where it has been for the past 30 years at least. The only thing that has changed is the sign now says "Aquarium Systems, A Spectrum brands Company" coinciding with Marinelands recent acquisition by Spectrum (formerly the Rayovac Corp)
Regardless, IMO, the Kent salt has not been as consistant as I have seen in the past. I, too, got some of the "zero alk" salt a while back. It has scared me away from trying another batch anytime soon.