Sorry - I missed that bit in your earlier post.
Sounds like Mycoplasma to me. I use Tylan 200 for that, not sure what others use or if Baytril is any good - go back to the Vet. I think you can get Tylan soluble, but it's not as good as the injectable - 0.5ml injected in the breast, if you see your "foreign" vet who isn't sure of British regulations you may be able to get him to give you enough to inject your birds yourself.
You never actually get rid of Mycoplasma, stress and things like that can bring it on - also one of the birds may be a carrier, but that needs another post
. They will, as well get over it on their own, but some may die in the process.
Goggle Mycoplasma and read about it before you go so you know a little more about it. Also April Country Smallholding had a good article on it.
PM me if you want to know more.