So I'm on my second lot of chicks hatching, the mother kicked three to death by mistake (or so I hope) and so i seperated them, now I just noticed that all of the chicks have a large growth on their chests! What is this?? Are they okay?? They all seem fine, no distress and they're all eating and drinking as usual but I'm so worried, I've already lost three of them 
The growths only appeared in the last few hours, theyre about the size of an egg yolk and the chicks are between one week and two weeks old

The growths only appeared in the last few hours, theyre about the size of an egg yolk and the chicks are between one week and two weeks old