About 12 hours ago, before they roost, she seems fine. But when I checked her 4 hours later, I can hear breathing heavily with tail bobbing, with slight coughing, and making sounds from her mouth whenever she breathes. I released her 5 weeks ago, after I keeping her in the cage, to let her foot pad heal after doing foot surgery, because of suspected bumble foot( luckily, I never find any pus). 8 weeks ago, I also dewormed her with albendazole at 1.5x-2x the recommended dose(20mg/kg) for 3 days( I have done it to my chickens before, and there was no negative side effects that are obvious), and I used oral Ivermectin 1 time dose, at dosage of 2-3mg/kg which is below the 5.4mg/kg toxic dose.. She currently lives inside a pen with the other chickens, and there are only few insects on that place. Could it be that she aspirated, when my rooster mate her, during the night, or she is suffering from parasitic or fungal infection? There is no other symptoms, and the rest of my chickens appear healthy. I just gave her fenbendazole at dosage of30mg/kg, and I am planning to give her 2 more dose for 2 more days.