Why won't my 4 (nearly 5) year old eat?

She ate 2 bites of her breakfast, none of her lunch, and insisited that she was not hungry at supper time. She did eat 2 hershey's miniatures around 1:00 today. And i managed to get about 1/4 cup of mac n cheese in her at about 7:30 tonite. This is not normal for her at all. She doesn't seem to be sick or have any symptoms. I am concerned though.