Hhmmm could be Lymphoid Leukosis see
http://www.poultryhub.org/bird-health-and-disease/lymphoid-leukosis/ This usually strikes birds at maturity and one of the symptoms is loss of appetite, emancipation. If so there's no cure and an autopsy should be able to confirm.
Below is a paste from
http://msucares.com/poultry/diseases/disviral.htm with relevant passages in bold.
"Lymphoid leukosis characteristically produces lymphoid tumors, particularly in the liver and spleen. The tumors may also affect other visceral organs such as ovary and lungs.
Affected birds may die without preliminary symptoms, but the disease usually is chronic in nature and
affected birds show loss of appetite, progressive emaciation and diarrhea. Clinically affected birds invariably die. Losses due to the disease are most severe shortly after onset of egg production, but losses will continue for as long as the flock is retained. Total loss may approach twenty percent during the life of a flock.
Clinical diagnosis of lymphoid leukosis is based upon flock history and disease manifestations. The lymphoid disease cannot be readily distinguished from the visceral response to Marek's disease; however, there are some features that aid in differential diagnosis.
There is no treatment for lymphoid leukosis. Although the disease cannot be prevented completely, there are certain steps that can be taken to help control the level of infection within a flock. Some steps are:
•Buy resistant strains of birds since genetic resistance is a deterrent,
•Brood in isolation and do not mix birds of different ages, especially through six weeks of age,
•Keep the incubator clean and disinfected,
•Control blood-sucking parasites,
•Good care, limiting stress, and adequate ration will be of benefit"
Chickens with lymphoid leukosis show nonspecific clinical signs including inappetence, weakness, diarrhea, dehydration, and emaciation. Infected chickens become depressed before death. Palpation often reveals an enlarged bursa and sometimes an enlarged liver. Infected birds may not necessarily develop tumors, but they may lay fewer eggs.
Best of luck
HF