trouble

Hi I am new to this forum, I have 8 cockatiels and they have tried to breed and sometimes the eggs haven't been any good but I get my chicks to about 3 weeks at the most and then loose them and I don't know why. Any help would be useful. Kind Regards Henry

Ok, Sonny is a 1 year old female. She can be really nice, snuggling up to my face and rubbing her head against my cheek,then suddely she starts to attack the **** out of my face and hiss. then she goes back to how she was before, this happens every few minutes. Or she is sat on the Cage or...