I've lost yet another chick! 4th loss in 4 days! I bought 12 chicks Friday. 2 Ameraucanas (healthy), 3 Black Australorps (healthy), 3 SLW, 4 Buff O. 2 BO dead, 2 SLW dead. Brooder conditions are good (temp good, fresh water and food, fresh bedding daily, etc.) Medicated chick starter only. Electrolyte water rotated with fresh. They become lethargic, don't want to move. Will eat & drink if done by hand, perks up, then dies. Just now noticed bloody runny stool on dead chicks vent. No others had that. What on earth is happening to these babies? Should I start antibiotics? What to do???