Chicken white watery poo please help

One of my chickens has had white watery poo for over a week. She is still eating and drinking and laying every day. She is under 2 years of age. On looking at her today she has normal poo at the end of this red thing hanging from her with this shuts stuff around and her feathers. Couldn't feel a crop she felt for just. She has lost her feathers underneath. She is still loving around happily with the other chicken. Recently had rat man out as had two rats around the chicken coop. Poison put out by not where chickens could have got too.
All other chickens fine no evident of mites anywhere.
Please can u advise what u think it might be will try to upload pictures.
Thanks Mojo02