As it happens life got hectic and I didn't get a clutch of eggs out of the aviary and they were hatched by the hens. The chicks started to die once again. It looked like one of the birds in the aviary was killing them. All the dead chicks had injuries mainly on the legs so once again I took the chicks and remaining eggs.
This time around I have had a chick die within a few hours of hatching in the brooder with similar symptoms to the dead chicks in the aviary. All of the chicks had bright red legs. I've lost chicks to pasty butt overnight and they haven't had this so I'm assuming it's a symptom of whatever killed them.

I've tried googling for possible diseases/bacteria etc that could cause this to no avail. Anyone have any idea what it might be? They are in the aviary with my gouldians who currently have some chicks so I'd like to sort this asap.