I am about in a panic. I have four laying hens and one Ameraucana pullet that survived the attack. The Ameraucana pullet was born May 6. We also have some juvenile birds born June 27 or there abouts. These are all barnyard mix, full size chickens. Of those, we have 5 to 7 males and 1 to 3 females (8 total, we just still have a couple that is baffling us). We also have 2 Silkie roos, brought home 2 Silkie layers, born in January, today. The girls are in a quarantine pen on our carport. We also have a rabbit and two ducks (khaki Campbell male and female mates). Just in case it could be related, we also have seven cats.
Anyway, I was putting the babies to bed, girls in quarantine, Silkie roos in their pen, rabbit is caged at all times and the rest live in the big coop. I noticed that for the first time for me, the teenagers were all on the roost, settled. All except one. This is one of my gender confused chickens. Gandalf the Grey or Gigi (depending) was being flogged and pecked by the big girls on the top roost. He went into a nesting box and I had to drag him out. When I tried to approach the roost, he panicked. I am used to placing them on the roost as I sing to them and they are quickly soothed as soon as the big girls stop pecking on them, but this was my first serious panic attack from them. So, I closed everyone up and brought the teenager in the house with me to listen to the rest of church service and wait for the rest to settle down so I could sneak him in. While I was holding him, I noticed that the sounds he was making was more like a raspy sound. I tried to listen to the lungs and didn't hear anything that sounded bubbly, but it was still a concerning sound. He also had his break open, panting. I couldn't tell if he was hot or having difficulty breathing. I adjusted several times to make sure I wasn't holding him too tight. I couldn't get a look in his beak because every time I would try, I would get clawed up as he panicked some more. After dark, we took him back out and ran our hands on the backs of the rest of the crew to get them to make a sound. The big girls all sounded normal. All of the teenagers, including the pullet, made this same type of raspy sound. At several points, something made a very loud sound that mimicked a dogs bark. Hubby thinks it came from the ducks, I don't agree but couldn't say for sure who it was. As I left, I noted that Gigi was still breathing, mouth open, fast shallow breaths.
Does this sound like a possible respiratory infection has rapidly spread through the flock, a gapeworm outbreak, or normal voice changes as the birds mature? I am very concerned about this as Gigi and the pullet are just two of my faves to keep and I have a few more that are sweet and gorgeous that I adore. But, if it's something contagious, I don't want my Silkies to get it or anyone else. It is so strange that the teenagers all sound so strange all at once. I also learned yesterday that none of the chicks available to buy through local feed stores are vaccinated for cocci or Mareks. All of the teenagers except the pullet were hatched out by one of our laying hens and we didn't know about vaccinating at that time, so also are unvaccinated. Also all unvaccinated for fowl pox. Sorry this was so long, really wanted to be sure I hit all the bases in case one or more animals could be causing this or could be nothing, but needed to let you know how widespread this is in my flock.

If this is an illness of some sort, what can I do to save them? We do not raise for meat and eggs were just a bonus. We initially got these babies to control the insect population since I have chemical sensitivities and can't use chemical warfare even if we wanted to. These babies are now our pets and beloved part of the family, so please, I would much rather try to save than kill them.
Thank you in advance for any and all help.