Beautiful babies! Any chance you could try some emergency measure for #4? It seems like if it hasn't hatched by now and it's still alive it might need help.... Or let nature run its course.
I did the same thing. Because of BYC I decided the day I received my newest chick shipment to switch to a radiant heating pad but had to use a lamp for the first three days. Heating pad was way better. The babies are so cute! Congrats! Hopefully #4 can pull through :)