My advice is dispose of the sick bird ,treat the rest with Vircon S ,one level tea spoon To 1 gallon of water remove grit And dont feed for 48 hrs. After 48 hrs give multi vits for 2 days And feed lightly .omo.
Ian I don't understand if your trying to build a family why are u training them ,if this is your breeding stock training them won't tell u if they can breed ? hope u get them back mate.