Sick hen open beak & making high pitch sound.

[candybeers2011]

My 1 year old hen is suddenly keeping her beak open & making a high pitch sound. I think I can also hear a slightly raspy sound when I put my ear to her body to check on her breathing. I'm assuming she must have some kind of respiratory issue, but it's the first time I've had a chicken become sick with something like this. I'm also fairly new to raising chickens being that this is my 2nd year having chickens. I've learned a lot and been reading lots of material about raising healthy chickens, but I'd really appreciate any advice from more experienced chickens farmers. I've isolated her away from the rest of my flock and they're all healthy still. I've given her poultry booster and I've been putting poultry cell in the water for my entire flock of 4 chickens from the beginning of having chickens just to give them extra nutrients to keep them as healthy as possible. They have plenty of room and they're all eating and drinking, including my sick hen. I gave her some boiled egg and she loved that today. I'm just so worried about what is wrong with her and I really need some suggestions on what to do and what this might be? She doesn't have any mites and is very healthy other than this mystery illness. Thank you in advance for any help!

 

[Eggcessive]

Is the sound she is making like the one in post 1 here:
https://www.backyardchickens.com/threads/silkie-w-possible-stridor.1218528/
I would probably put her back in the flock with the others for now. If she has stridor like in the video, it may go away in a few hours. That can happen if a small piece of feed gets into the airway. If she has a respiratory infection, then the others would already be exposed. Let us know how she is doing later.