This is the reason why I suggested removing all the fish from the planted tank and treat seperately. The plants, snails, shrimp will not need any treatment at all, just higher heat to accelerate the life-cycle of the remaining Ich.The invertebrates will not contract ich so it is safe to remove them out of the tank. Even though salt will not hurt the snails when you dissolve it, it would be safer to remove the snails out of the tank. Though the trophonts might end up trapped inside the shells of the snails, the snails will not be affected by it at all. By 48-72 hours, the trophonts eventually die due to lack of hosts (assuming the snails are placed in a fish-free environment).
The fish would be treated with just salt and heat, and will only take a week to cure.
Of course Lupin makes it easier to understand! :thm: