What's wrong with my hen? Please Help!

Hi, I am starting to worry about my Columbine hen. At first she appeared to have hiccups however now i believe she is ill. She often makes a 'hiccup' type noise then wheezes when she inhales. When she makes the noise she also moves her head in a way that looks like she is clearing her throat. She has been doing this for around a week now. Apart from this she is healthy and happy, she has clear eyes and is alert and eating and drinking well. I have done some research and am wondering if it could be gape-worm and if so what treatments are available? She seems to make the noise constantly for about 10 minutes then stops for a while then starts again. Should i be worried about her? Also, my two other hens are fine and healthy so I'm hoping its not contagious. Please help! ChickenLotts.