I think it was coccidia. Even with medicated food, and on wire they can still get it, don't know how but they do. Treat with Corid. When birds are that skinny, their body starts to shut down, organs fail - (think what happens to anorexic people) they have trouble maintaining body temperature, so I put them under a light. When they get so weak, they can no longer swallow, their body has pulled out all nutrients and they start going into a coma from lack of blood sugar and organ failure etc..., their body starts to arch back, pupils widen and then death. this is why you little chick looked like he was arching back his neck. So sorry you lost them.....