I'm going to prematurely offer some guesses and advice, but still need to see photos of the debrided wounds. (Debride means all dead, extraneous tissue removed.)
The use of the word "goo" to describe the wounds indicates infection - festering wounds that bacteria are preventing from healing. Perhaps these chickens had a run-in with a predator or a barbed fence or frayed chicken wire fencing.
Other skin lesions such as skin tumors wouldn't cause festering/pus. Skin parasites would cause dermatitis. I suppose the skin could become infected, but I haven't heard of it producing such wounds as these.
If I don't get back here today, this is what I would recommend as treatment for infected tissue. Clean wounds thoroughly every day, scrubbing lightly with a wash cloth to remove dead and tissue that is not viable. If you look closely, the difference between living tissue and dead and non-living tissue will be obvious. Live tissue has a healthy color and is warm. All other tissue if not removed acts as "fertilizer" to breed bacteria, so needs to be removed when treating large wounds.
After cleaning each day, coat the entire wound with Triple antibiotic ointment or Neosporin. Examine the wounds later on to be sure the ointment hasn't been worn off and reapply to keep the wounds covered with ointment at all times. If allowed to become dried out, bacteria will attack and healing will stop. Infection will return.
Pain may be a factor and causing poor appetite so a chewable aspirin twice a day may be given for pain management. Restore glucose levels with sugar in the water for a couple days, and feed high grade protein to put some weight back on the patients.
If they continue to act lethargic, an oral antibiotic may be necessary as the infection may have gone systemic in the bloodstream. From your description, these two may be quite sick. If they are so far gone that their immune systems have been seriously weakened by the infection, they could die in spite of all you do. Going from your descriptions, I give them 50/50 odds of making it through this, and it would only be because you worked hard at saving them with diligent wound care and feeding.
