It took me a little while to figure it out but it looks like Amazonia ver. 2 is basically less heavily loaded with nutrients than the original. It comes with a little package of root tabs to compensate. I think they probably needed a product that was more forgiving for people who were stepping up to the active substrate game. Either that or it was a supply chain/manufacturing issue. There is a post on the ADA website from a couple years ago about how they have been having trouble with production.