Odd Behavior

I have two hens that, after the initial quarantine, keeping an eye on them, worming, etc. they were released into my small flock. Lately, I have noticed that one of the hens, a year or so old Buff Orpington, will slightly gasp when she breaths, it is not very noticeable, you have to stop and watch her to catch it. This morning I caught her to look her over as general outward appearance, she is bright eyed, her comb is a nice red color, she is eating, drinking and doing normal chicken things.

While holding her she really started to gasp. Her comb darkened up noticeably, so I listened to her lungs and I believe I do hear some raspy sounds but she certainly doesn't wish to be fussed with at all. Her vent is very small and dry looking, so I don't think she is laying at all. Her counter part that she came with, a beautiful standard black laced wing Cochin hen, is molting but acting normal.

Anyone have any ideas as to what to do? I worm my flock once a month with wazine, keep a clean coop, clean their large yard and rake it every few weeks, they get fresh water each day and their feed is cleaned and they never get anything more than they could eat.