I agree with melodrama, also red mite which they may have taken with them. Hens moult in different ways and can look rather naked at times too, so you may like to give them something to support this.
A general tonic in their water like herban or apple cider vinegar with some garlic, should help support their immune system & deal with any nasties.
He breathing may mean she has a cold or catarh, the first thing I would use would be a drop of eucalytus oil or other decongestant - a drop on the back of her neck ( should act as an insect repellant too).
Also check her crop? perhaps she has sour crop? If it's not worms it may be something digestive. Though as she's active this may not be the case.
For this I would use Epsom salts or liver salts - diluted ( I'd have to check on ratios) and would feed it to her from a spoon or syringe. Maybe some medicinal charcoal too or slippery elm mixed in a mash. I have had success with homeopathic treatment too. But at times like these it's best to use what's in your cupboard or is easily available.