Help! My Chicken is sick

I think one of my chickens is sick.  She is sitting around alot, sometimes not even coming out of the hen house, although she is not sitting on the perch, just on the floor.  She is not laying but is definitely eating and drinking although not sure how much.  She is making a 'growl' instead of the normal 'cluck'.  Any ideas?

Please help! I think my chicken is sick.  She is not laying, making a 'growling' noise instead of a 'cluck', her comb is not sitting upright, it leans to one side, she is sitting on her own either outside of the hen house or in the nesting box, or even on the floor of the house, this morning she was not even sitting on her perch?  Is she sick? We have another 2 hens who seem unaffected, should I move her?