I have a chick that is 5 weeks old. 2 days ago her face was swollen. She then started sneezing yesterday and became lethargic. I have isolated her from the flock and started her on Tylan 50 injections. Today her face is no longer swollen but she is still lethargic, puffed up and has green poop. Any ideas as to what I am trying to fight? She is eating and drinking.