A member of our club has been having problems with his birds for sometime now, the birds just dont seem right. He has treated birds for Canker/cocci, have been tested for clamidia negative, the birds have yellow spots/marks on the backs of there tongues, no excess mucus in mouth, once birds are on Doxy they come right, once off they are back down again. The birds seem to fly/range very well around his loft and are keen to get out. His words are "they seems like they have lost there brains", as when he tosses the birds they are usually very very late back to the loft. Stress has been suggested, however once the birds are up on doxy they fly good, cancelling that out in my opinion.
Also birds he has bred for other members show none of these symptons in there lofts.
Hoping someone has experienced a simiilar problem or know of someone who has and can offer a solution.