Hi everyone,
For those of you that are having this problem, do follow chookchick's advice!
I had the same exact thing happen with one of my chicks this year. I thought for sure we were going to loose her. I seperated her so she could rest and made sure she had access to the heat lamp. I used organic apple cider vinegar in her water and within two days she had bounced back. The only thing I did different was dip her beak in a warm honey water solution about once an hour or so, which I found out later could have been a mistake. The poly-vi-sol without iron is great! I also gave her scrambled egg to try and get her eating. I was able to eventually get her to eat some organic yogurt with added probiotics by dabbing a bit on her beak with my finger.
Please make sure they are drinking, and dip their beaks from time to time in the water, being super careful not to get it in their nostrils. Keep checking for pasty butt, and remember that a tiny bit of poop can get dried in the vent opening, so make sure that the vent is opening all the way when you clean them.
My chicks are three weeks old now and everyone is doing great.
good luck!
Andrea