It started around evening, on Wednesday, I noticed one of my chicks are extremely lethargic, sitting with her eyes closed under the brooder heat lamp. Weak cheeps. Her brooder pals are all appearing healthy, though up until now last night. I found two more are having the same symptoms. I took chick #1 to the vet yesterday afternoon, and they are holding her there for testing and observation, giving her meds/fluids/antibiotics. She hasn't recovered yet, and no improvement as of today. I hope for the best at this point. My chicks are almost a week old. What should I do for them??