Hi there,
Check ventillation is adequate in the house.
Check there is no smell of ammonia in the morning in the house.
Check they are wormed (Gapeworm gives a tracheal rattle / cough).
Check Lime has not been used to clean a house or pen recently.
Micoplasma Gallisepticum causes respiratory problems as a secondary infection but can usually be helped by antibiotics - Tylan or Baytril are the most popular. You will need a trip to your vet to have the bird diagnosed and a prescription for the antibiotic. Note, you can buy the antibiotics online with a prescription cheaper. Eg from
MedicAnimal for example
There are several potential causes including infectious bronchitis virus, infectious laryngotracheitis virus, pneumovirus, pasteurella, aspergillus, irritants from cleaning products and so on.
If you suspect any of the above, it's best to go to a good poultry vet. There is a list of UK
poultry vets on the site.
Hope this helps.
Tim