Four days seems like a really long time, especially when one is already dead. Are there no Tractor Supply stores near you, or a co-op/farm store of any kind? Where do you get your chicken feed at?
This says: "The disease has a high mortality rate in baby chicks and death usually occurs within...
You can get Corid at Tractor Supply, or any farm store probably. I recently found some but it was with the goat medicine. In the chicken feed area at my local TSC they also had a special Corid feed, but it was more expensive for a far lower amount of medicine. If you buy the regular medicated...