Sounds like they might have contacted one of several different poultry diseases ie parathyroid, bird flu, chickenpox, and the list goes on. Some are treatable but not cureable (couriers) while others are cureable.
Some things to check for besides the wheezing, green or yellow runny stool, rapidly blinking eyes (thirst indicator), loss of scales on legs, unseasonable moult, discolored combs.
I would feed Sulmet (Sulvet?), available at most Farm Supply Stores, at the rate of about 1/2 cup to 3 gallons of water. Sulmet is a good all purpose antibiotic for poultry and other livestock. I use in for all my livestock, Goats, Sheep, Chickens, Turkeys, Pigeons, and Rabbits.