I have four, now three layers, one black rock about 4 now, and three rescued battery hens now about 2 1/2. One of the ex battery hens was dead this morning 
. She has not been well for a couple of weeks, but I have not been able to get to the bottom of it. She was very thin at the end, breast bone felt razor sharp, but her eyes were still bright, comb normal bright red colour and standing upright, although not as active as normal no visible diarrohea, no nasal discharge or cold symptoms, plenty of layers pellets and fresh water available. I clean out the house weekly, and change the nest box material twice a week or more if needed, I use fresh dry shredded paper. Only my blackrock is laying at the moment, in fact all birds laid well throughout the winter, but all the rescues stopped laying in late spring. They free range, either in their very large enclosure which is full of thik grass, or they are out "long ranging" in our three acre smallholding. One other rescue hen has always been susceptible to having white diarrohea, she is looking/feeling a little thin too but is behaving normally. Any ideas? I am stumped.