I have a 3 week old white plymouth rock. She is part of a flock of 10, 2 of which are white plymouth rocks. These 2 seemed to be the quickest growing, biggest eaters and most active. Now this particular one seems to spend alot of time just hanging out on the perch rather than investigating the brooder and scratching for food like the rest of the chicks. She does eat and drink periodically but not like the others. Her eyes are clear, no pasty butt, no breathing issues, etc. The other chicks go crazy when I treat them to a meal worm and she acts disinterested. I can't find anything visibly wrong. The are on medicated chick starter. I keep their waterer refreshed 2-3 times a day. Their brooder is cleaned on a regular basis. Being my first batch of chicks, I'm worried that she may be suffering from an illness I don't know about. Any suggestions?