I am not an expert on chicks with neurological symptoms, but there can be difficulties with infection from incubators, and vitamin or mineral deficiencies in the parent stock. How do you disinfect your incubator and brooder before each hatch? Incubator temperatures and humidity are also important. When I used to incubate shipped eggs, I found that the rarer breeds had poor hatches,while the more common breeds. I had better suspccess with broodies hatching my own eggs. Very sorry for your loss.