So, do you want any help or not? I'm not sure why you made your second post unless you lost the chick. It can take time for someone to see your post to help. Some who read posts may not feel comfortable enough to answer on the forum.
Sorry for your loss. If you see any symptoms in any of the others you may want to purchase some oxytetracycline in a packet to add to the water. That can treats symptoms of bacterial and mycoplasmal respiratory diseases.
Oxytetracycline is normally given in the water for 7 straight days. Depending on the brand dosage may be around 1 1/2 TB per gallon of water. Plain yogurt or probiotics can be given during and after treatment. Good luck.