For context, I have a school of Congo tetras that sometimes have mouth fungus that vanishes on its own. I've treated with praziquantel and Kapanplex separately in isolation, one time each. Any infection normally affects only the Congos and it lasts for 3-4 days each on the mouth, and then disappears. This is the first time any other fish beyond the Congo tetra has shown any symptoms. I also have another dwarf flag, a large polypterus sengalus, a large aeneus corydora, a worm-jawed morymid, a large african butterfly, and a pleurops synodontis. None of these have shown any symptoms.
Thanks again folks.