I had only one chick hatch on Dec. 23rd. So one week later (Dec. 30th), I bought 3 more to keep her company. Don't know the exact age of chicks because breeder had several different ages in the same box. But they are a least, 4 to 6 weeks old. My chick and one of the ones I bought are almost fully feathered and getting quite large. But the other 2 chicks I bought, are still very tiny and only have their wing feathers. Is this normal?