You know I just lost a cherry barb overnight to that disease. On the other hand, I had a Gourami that had it for months getting better and worse constantly (I euthanized her today - so sad). Remove them to another tank or a large glass bowl with a air bubbler, no substrate so you can see if they are pooping - don't feed them except par-boiled peas (peeled and probably mashed for them since they are small fish. Get some Epsom salts (scan this forum or the Internet for Epsom salts and fish for the quantity) - they are really magnesium sulfate - not salt at all so make sure it is pure medical Epsom salts. They act as a mild laxative because they need to poop to remove some of that pressure on the swim bladder. Alternatively, expect the worst and euthanize them now. Mine's death was very sudden - just as you describe, unlike my Gourami that took months. My barb also had a much more severe case of it than my Gourami ever had.
Best of luck but I did spend a small fortune to try to keep my Gourami alive so if they look like they are under any distress go ahead and euthanize.