Of my three almost 6-month-old chickens, two have started laying and one hasn't. She isn't swollen; her breathing, appetite, activity level, and feces are all normal. Today though, she sat in one of the nesting boxes and clucked up quite a racket, but didn't produce anything. Is it normal for chickens to have a "false start" or should I start worrying? Thank you in advance for any feedback.