What's going on with my ducks?

[Cluckycleaner]

I'm new to duck raising and for some reason a few of my 10 young Indian Runner ducks are losing some of their facial feathers and some are also vomiting. I feed them Flock Raiser feed and change the mucky water container twice a day. Should I separate the sickly from the healthy? Any helpful suggestions or diagnoses would be appreciated.

 

[ducksinarow]

Do they have enough space? Ducklings will pick at each other if crowded.

 

[Cluckycleaner]

they were crowded in a small pen until about 2 days ago when I made them a larger day use pen. I still lock them up at night for their safety though.