I have a week-old chick who squeaks when she inhales. She doesn't do it all the time, but when she's peeping she peeps on the exhale and squeaks on the inhale. Sometimes she stands there and you can hear her squeaking with every inhalation. She is active, eating, drinking, and otherwise behaving normally. I noticed a hen doing this the other day too, but haven't heard her again. It was a very hot day when I first noticed it. I've never heard this before in my few chicken-keeping years. What is it? Do I worry?