These are my first time raising chickens. I purchased 6 chicks. Everything seams fine babies are growing but there is one that is smaller than the rest. She might be a week younger than the rest was my guess. The reason I'm concerned is she is so sweet! She lets me pick her up with out fuss, lays in my hand and when I pet her she closes her eyes. None of the other chicks act like this.. Is this a sweet lady bird or is she sick? My chicks are about 4 or 5 weeks old.