This is my fifth time with mail order chicks and I have never had anything like this happen. We received 21 chicks in the mail, but 2 were weak and we couldn't revive them and died the first day (nothing out of the ordinary.) I had them on electrolyte and vitamin water for first three days while they were on puppy pads too. After that, I switched to normal water and puppy pads with large flake pine shavings on top. Around this same time one chick previously doing well suddenly started labored breathing and passed away within hours. Now yesterday, (my 4th day having the chicks) one of the previous healthy chicks suddenly dropped over and laid down for a little bit, twisting it's head upwards. Within a minute or so it was up (yet a little shaky) but eating like the rest if them. I wondered if it wouldn't make it through the night, yet did, but there was a different chick dead in the brooder! I noticed absolutely nothing previously wrong either. I am just worried that this might occur again and I'm at loss as to what is going on. They were from a NPIP certified breeder, but have not been on medicated food, just the normal Nutrena starter. I clean the brooder which is about 16 square feet minimum of 2-3 times a day for the now 17 chicks. There are no drafts either and the bedding while sometimes gets soiled, is never dusty or damp. Help!