again these are idea's that can help assist the op and different people have different experiences with different fish and at different stages.
Bad advice is bad advice, I don't care how many times it's repeated on the interweb by those who have zero background in disease & treatment of finfish. My comments are not just based on personal opinion, or personal experience, but are based on the professional opinion of those who are considered experts in this field. A couple of experts that come to mind would be Dr. Ruth Francis Floyd, from the Florida State University, and Dr. Edward Noga, from the North Carolina State University.
You can find the credentials of both below;
Ruth Francis-Floyd, DVM, MS
Professor Aquatic Animal Health Program Director
Fisheries and Aquatic Sciences
Large Animal Clinical Sciences
Certified Fish Pathologist, American Fisheries Society, 1989
Diplomate, American College of Zoological Medicine, 1998
Edward J. Noga, MS, DVM, is Professor of Aquatic Medicine (College of Veterinary Medicine) and Adjunct Professor of Zoology (College of Agriculture and Life Science) at North Carolina State University, in Raleigh, North Carolina, and Adjunct Professor of Marine Science (Center for Marine Science) at the University of North Carolina in Wilmington, North Carolina.
Both have been published in peer reviewed journals numerous times, and Edward Noga has one of the most comprehensive books published on the subject of fish disease, diagnosis, & treatment that I think one can find, at least in North America. Neither of the above experts recommend salt (sodium chloride) baths, or adding salt to the aquarium water of a fish that is suffering from spironucleus/hexamita. What they do recommend is treating said fish with metronidazole, and/or treating orally with magnesium sulfate. (epsom salt)
This isn't some kind of pissing contest oriqua, but unless you can direct me to where an actual expert on this subject has recommended adding sodium chloride to a fishes tank water, or treated in a salt bath, when a fish appears to be suffering from an outbreak of internal flagellates that are residing in their gastrointestinal tract, and in advanced cases have possibly already travelled to one or more internal organs, I'm going to have to strongly disagree with your armchair advice.
The OP can draw their own conclusions as to how best to proceed with their fish.