Anything that can help their immune systems, like vitamins (Nutri-Drench or Poultry Cell), keeping their coop and run clean and dry, and not overcrowding. I, personally, wouldn't do antibiotics unless it becomes more severe. My flock is MG-positive (a life-long bacterial infection) and I don't treat unless the birds look miserable. You could have a test done to confirm what it is exactly that they have, but that is expensive. I only did it because I wanted to know what to treat with and I also wanted to sell birds, but that's not going to happen now that I know the diagnoses.