Just catching up Nadene sorry you are having a problem, are they your show stock? Have you found out any more/ lost any more (I hope not). It's awful when you can't find the problem, are they babies or older birds? check seed etc to see if that's a factor. Hope you find the answer soon.
Thanks Robyn, yes they have all been my show stock so far. Touch wood no more are showing signs of illness. It has gone through all ages from 4 months to 6 year olds.