Greetings, I am Dr. Pat. I have worked with birds exclusively for many years.
I am sorry no other expert has taken your question. We all come online at different times, I have just logged in and saw that you have not been answered. I hope I can still be of assistance.
More photos are always good.
At first glance it looks like these spots may be from flies or other biting insects. What is your geographic location and local weather?
Do the hens peck him?
Any lumps around the mouth or face?
They can also have sunburn, parasitic diseases, nutritional issues associated with comb problems. If circulation is impaired for any reason, the tips of the comb can turn dark and eventually drop off. This can also be an indication of serious systemic disease.
For right now, clean the comb with sterile saline, and apply a small amount of fly repellent (avoid the eyes and the open areas); you can find it in the equine section of feed stores, spray some on a wash cloth and wipe his head and neck. If you can convince a pharmacist or vet to sell you 1% silver sulfadiazine cream, apply it twice a day to the lesions. Do not use anything else.
Can you tell me more about the bird?
How long has this been going on?
How long have you had him?
Where is he from?
Any accidents or trauma?
Interactions with other birds/pets/children/guests?
What is the usual diet? has it changed recently?
Has the bird gotten into anything? Does he poke his head through the fence?
If you feel comfortable with it, examine the bird thoroughly, using gentle restraint via washcloth or hand towel: do not restrict the chest or hold around the body. Check the eyes, nostrils, mouth and beak if possible, having a good look in there for mucus, redness, masses or anything else unusual. Palpate the tummy for pain, fluid, lumps or anything else. You can take the temperature gently with a rectal thermometer. Anything above 105F/40C is significant. Check all the joints for swelling, pain, and mobility. The feathers should be parted to view the skin, muscles and skeleton below; this can be done using a q-tip with isopropyl alcohol or KY gel. Look for bruising, lacerations, injured feathers.
I know it is expensive, but you may not have many home options, because the first thing you need a vet for is to find out what is going on. Treatment is only as good as the diagnosis. If you call around, you may find a vet to work within your means.
She needs to see an avian/poultry-experienced veterinarian ASAP for complete examination, diagnosis and appropriate treatment. Check
https://aav.site-ym.com/?page=basiccare click on "find a vet"
for members of AAV in your area.