Odd croupy noise from our 24 week hen

Hi there - this morning we noticed one of our hens is making this wheezy noise when she inhales or exhales (can't tell which). It is constant if she is just standing around. If we feed her treats, she will happily gobble them up and not make this noise the whole time she is eating. When she stops, this noise starts again. She appears to not be in any distress though - the sound is just worrying us. Thank you for your help!!!! She is 24 weeks and has not laid any eggs yet - tried to feel around to see if she is egg bound but can't feel anything (this is our first time ever having chickens and none has laid yet).