Not sure at all--It can be extremely difficult to pin down an exact, correct diagnosis for a poultry disease, especially without vet help. It is optimal if you know exactly what you're dealing with, but often you can treat successfully without knowing for sure.
It can often help to just try some inexpensive antibiotics & see if they help whatever the problem is. Try one kind of antibiotics for 5+ days or however many are recommended in instructions. If no improvement, switch and try a med from another class of antibiotics.
I believe there are 3 general classes of antibiotics for chickens. 1 class includes Aeromycin, Terramycin, etc. 1 class includes sulfa-type meds. And I'm not sure about third.
Anyway, you can get a pouch of Aeromycin or Terramycin powder to add to water for about $4 at a feed store. I've seen a sulfa-type med at a pet store in the pet birds (parakeets, etc.) section before.
The Chinese herb Astragalus, which you can buy in capsules at some health food stores, is also supposed to be a good immunity booster.