Hi
These things are usually viral, so you need to keep them isolated or risk it spreading to your existing flock. Viruses need time to run their course. I use eucalyptus oil or Vick's Vapour Rub on those that are struggling with their breathing to help open the airways. Just a little rubbed on their comb and wattles and under their beak (throat area). Vet RX is a product specifically formulated in the USA to help with these sort of symptoms in poultry and whilst it can be ordered off Amazon, it's quite pricey with postage, so I still haven't tried it.
Hopefully they will get over it in a couple of weeks without any secondary infections setting in. Good luck with them.
Barbara