I have a RIR that has isolated herself from the rest of the flock and she is sitting in a strange way. I have checked to see if I could feel an egg, but It was soft, Crop seems to be in order, and vent looks clean, aside for her feathers around her vent looking a little messy, I can't see anything wrong. She just started this behaviour this morning, She is one of my more lively chickens so I know there has got to be something wrong, any advise??