Could be from an injury, it's really hard to tell, there's a darker spot that almost looks like a scab.
Show more photos of their birds and overall condition.
Check them over for lice/mites.
Provide them with good loose dirt for dust bathing.
I would be tempted to just watch that area close and leave it untreated at this time since I would suspect moisture from ointments/oil under the wing may actually do more harm than good.
How old are these birds? They may benefit from 18-20% chick starter or all flock feed and poultry vitamins once a week as well.
Show more photos of their birds and overall condition.
Check them over for lice/mites.
Provide them with good loose dirt for dust bathing.
I would be tempted to just watch that area close and leave it untreated at this time since I would suspect moisture from ointments/oil under the wing may actually do more harm than good.
How old are these birds? They may benefit from 18-20% chick starter or all flock feed and poultry vitamins once a week as well.