I just brought home an Orange shoulder adult today and could not help myself in reseaching into the issue... I found this information at and I believe JHemdal already mentioned this disease after re-reading the forum
http://saltaquarium.about.com/od/otherdiseases/Bacterial_Fungal_Viral_Other_Fish_Diseases.htm
http://saltaquarium.about.com/cs/compldiagnodisease/a/aa042801.htm
I can only hope that this points you in a different direction to finding out what is wrong. This link has much more information about other possiblities. I am not an expert, just taking the time to see if I can find different information on our never ending web and to educate myself.
Other Fish Diseases
Marine Fungus
Other Names: Ichthyophonus, CNS Disease
Symptoms: Darkening in color, sandpaper appearance of skin, poor appetite, listlessness.
Comments: This disease is usually associated with stress, sometimes brought on by poor water quality. This is not a very common disease and treatment is very difficult. The fungus is usually introduced into the tank when adding new animals.
Treatment: Treatment for this disease is difficult. Improve the environment and remove any possible causes of stress. Try a proprietary anti-fungal medication in a hospital tank. Food soaked in phenoxetol can also be effective if the fish is eating.
Prevention: Insure good water quality and temperature parameters to prevent animals from getting stressed. Stress breaks down the protective mucous coating on a fish and allows the fungus to gain a foothold. Additionally, any new fish should be given a short freshwater bath and kept in a quarantine tank for two to three weeks before being introduced into the main aquarium.