Feather breakage and itching...

[CharlieBaby]

Hi there, I'm trying to figure out the cause of persistent feather loss in two of my 3-year-old hens. Both have been excessively itching around their necks for over a year. Their feathers break off or fall out in the same spots they scratch. Feathers grow back normally after molt but are quickly lost again. The feather loss isn’t due to pecking or a typical molt, and I’m unsure whether both hens are dealing with the same root issue. Photos attached (lots!).

Pippy (tan, Salmon Faverolles):

• Bald neck and partially bald chest
• Scratches this area frequently
• Chronic vent gleet that has resisted multiple treatments
• Still laying, but shells are somewhat thin

Stella (white, Delaware):

• Feathers break/shafts strip where she scratches with her foot
• Smells like wet dog when feathers are damp
• White feathers are yellowed/stained around neck
• Previously had vent gleet (now cleared)
• Has stopped laying after soft/misshapen eggs
• Also has some respiratory symptoms (possible MG or IB)

I started by treating for mites and lice even though I have not seen any lice or mites upon visual inspection. When this didn't solve the issue, I switched to treating topically for yeast infection. This is not bullying, mating, or a typical molt.

Tried for possible mites/lice:

• Sprayed hens and coop with Elector PSP (more than once)
• Sulfur powder on feathers and in dust bathing areas

Tried for possible yeast/fungal infection:

• Antiseptic and antifungal medicated shampoo (ketoconazole and benzethonium chloride)
• Topical clotrimazole cream

Tried for vent gleet:

• ACV in water (1 tbs per gallon)
• Probiotics and non-dairy coconut yogurt
• Miconazole cream (oral)
• Acidified copper sulfate in water (5-7 days)

Diet/environment:

• 17% protein layer pellets
• Fresh "mush" (layer feed with water)
• Fresh water (occasional ACV, electrolytes, vitamins)
• Free choice oyster and egg shells
• Minimal treats, supervised free ranging
• Spacious run with areas for climbing, perching, dust bathing
• Pacific Northwest

I may make separate posts later for Stella’s suspected reproductive and respiratory issues and Pippy’s chronic vent gleet, but wanted to focus here on the feather loss and excessive itching.

What do you think is causing this persistent feather loss, and what can I do about it? Maybe depluming mites and time for ivermectin drench? Persistent yeast? Something else?

Thanks for reading!