Hello. I am sorry to hear that your chicken is having problems. Here are my thoughts on the various signs you described and what could be going on.
1. There can be multiple causes of the abnormal flaky skin. Some common causes would be skin parasites such as mites, a nutritional problem or a bacterial/fungal skin infection.
2. The shriveled comb can be due to the skin problem, nutritional problems and/or associated with other problems such as internal parasites which can loss a loss of blood.
3. The lack of energy can also be due to anemia which is a condition where the animal does not have enough red blood cells due to various issues.
4. Finally, the weight loss despite a good appetite can also be due internal parasites and/or an improper diet as well as conditions such as exposure to poisons such as lead, a serious bacterial infection and other problems.
In summary, skin or internal parasites, lead poisoning, nutritional problems and bacterial/fungal skin infections would be on the top of my list of potential problems to investigate. Your chickens may be experiencing one or more of these problems.
So, I would recommend the following:
1. Please let me know what type of food you offer your chickens and whether you provide any vitamin or mineral supplements. I can then determine whether you have any potential nutritional deficiencies.
2. I would thoroughly clean out your chicken coop in order to reduce any potential parasite load. The cleaning process involves a two-step process including a hot soapy water scrub and then applying a dilute bleach solution (1/10 dilution) and letting it sit for ten minutes before rinsing it off with water. Exposing the structure to direct sunlight for a day or so after cleaning will also help kill any parasites.
3. I would recommend you contact local experts to help guide you through dealing with this problem. You can contact your local agricultural Co-op and/or farm/avian veterinarian to test your birds' feces for both external and internal parasites as well as exposure to toxins such as lead. They could also examine your animals for signs of skin infections. I have attached a link you can refer to in order to look for a local veterinarian who is familiar with working on birds.
I sincerely ***** ***** answers your questions. Should you have any further questions or concerns please let me know. I wish you and your chickens all the best.