im afraid ,[in my opinion] thats 3 birds now,,,,sorry to say, something very far wrong ,,,,its a.s.a.p for good avian vet,,,,,either for a pm , or their own test, they will advise, but seperate them from the rest, and keep every thing clean , disenfectanted,,, and allways wash hand etc,,,,wish you luck , but you must get to the bottom of it ,,if youve other birds