Without knowing what you're treating, it's hard to say that any specific product will work.
Have you ever seen ammonia levels? If all these animals have been added within the last month, I'd be shocked if there wasn't a spike, even with fishless cycling and a lot of plants. But, more likely, one of the fish (rummynose get my bet, since they're the first to show symptoms) brought something in, and the ammonia levels spiking have stressed and weakened all the fish to the point where they're susceptible. Water changes will be your friend, as will getting the test kit results confirmed by a 2nd party. Perhaps an LFS where you purchased fish?
Have you ever seen ammonia levels? If all these animals have been added within the last month, I'd be shocked if there wasn't a spike, even with fishless cycling and a lot of plants. But, more likely, one of the fish (rummynose get my bet, since they're the first to show symptoms) brought something in, and the ammonia levels spiking have stressed and weakened all the fish to the point where they're susceptible. Water changes will be your friend, as will getting the test kit results confirmed by a 2nd party. Perhaps an LFS where you purchased fish?
