Would you dose salt with that approach? I’m one of those “always tries salt before reaching for other meds” people.
Salt has limited use, especially in a planted tank (while more tolerant plants will survive, many more delicate leaf plants won’t) and few people dose effective levels of salt
Of course if fish survive (whatever ailment salt was dosed for), then most will assume a cause and effect ie “salt cure”
There are some fish which respond very well to salt treatments - in part as they are well able to tolerate the increased salt or have conditions which respond well to the salt treatment
(eg, angelfish, discus, guppies depending on ailment, but if keeping fish from natural soft, acidic waters, likely replicating these conditions would be more beneficial (especially if pH < 5.5) )
While salt can help with Nitrite toxicity and some external parasites, it’s not going to have much impact on internal (bacterial) infections
Once lemon tetras are isolated, I might use a combination of Epsom salts and sodium chloride salt IF I couldn’t source more effective treatments, if fish are eating and medicated foods are an option, I might also add these salts to see if fish respond to the osmotic support