Others may suggest differently but in most cases, conjectured use of antibiotics in cases of only dyspnea, and no other symptoms like nasal/oculur discharge are contradicted due to the subsequent susceptible environment of the respiratory system which may allow the growth of fungi like Aspergillus to flourish, and make the problem severely worse. Before antibiotic use, a culture taken from the trachea to identify if bacteria is a concern would be a safer route to take.
View attachment 2427716
The abnormal sounds your hen is making is suggestive that there is something blocking, and interfering with her breathing, and her syrinx from producing sounds. Whether that be inflammation in the trachea, fungal spores growing inside, or a piece of material in the trachea it's impossible to tell without diagnostic procedures. If I were to guess, I would have to go with the material in her trachea, as it's likely her condition would be worsening with a bacterial, or fungal problem not getting better.
There is not much anyone can suggest over the internet, so if she continues to do the sounds, a vet would be your best bet.
https://www.metzerfarms.com/Veterinarians.cfm?CustID=27535705
.
