We had 12 chicks. Two died about a week apart and more are acting strangely. They stand around with their feathers puffed out and my daughter said that most of them are vomiting. They are with their mother and the rest of the flock. I am not sure how old they are. 4 weeks maybe. I was feeding chick starter from TSC but I just realized that it isn't medicated so I went and bought some that is medicated and some sav-a-chick. Their poop seems normal. Any ideas?