Rooster has laboured breathing, a very diminished crow, a darkened comb, and lethargic behaviour

Hello!

This is not my ideal first post but I'm in a bit of a bind as there are not many vets who deal with poultry in my area.

My rooster is about 8 months old and has seemed perfectly strong and healthy until a few weeks ago when he deteriorated almost over night. I've listed the symptoms below:

- he hangs and twists his head at awkward angles
- his breathing is laboured, he looks to be gasping for breath
- he still eats and drinks but his appetite has diminished
- he no longer crows, he only clucks strangely
- his feet are sometimes cold
- his comb has darkened
- he is lethargic
- he no longer climbs the ramp to the second level of the coop

More info:
- his crop seems normal
- he does not seem to be constipated and his droppings look normal
- there are instances where he seems perfectly normal but these are few and far between
- we have him on a broad spectrum antibiotic and a de-wormer

I've uploaded a video of him: https://www.youtube.com/my_videos?o=U



You can really see him struggling to breathe around the 1:00 minute mark.

I hope someone here can help!