Apologies in advance if this has been addressed. I searched previous posts and couldn't find one that fit my situation as closely as I'd like (mites, lice, vent gleet, feather picking, etc). We have 5 RIR hens, 2 yrs old. Behavior among all 5 currently normal - foraging, dust bathing when ground not frozen, laying (although not sure who is laying and if one is not - we get 3-4 daily and occasionally 5). Pecking order isn't anything extreme, no ganging up, etc. I do not witness feather picking, although I'm also not with them all the time. Ok, symptoms: noticed one hen with slight irritation on front of neck with slight feather loss about 7 days ago, sprayed with Poultry Aid. Over the past week have sprayed once or twice a day, a bit more feather loss down chest but no further than crop area, and the loss seems to have slowed or stopped. The irritation isn't wide-spread, in other areas of loss the skin is normal color. Thought mites/lice but cannot find any evidence. Then thought maybe molt, she did not go through a full molt last fall as did 3 others, but no other noticeable feather loss. About same time I noticed another hen with an irritated vent area plus feather loss (doesn't extend to belly) but believe she is still laying. I have been spraying her as well with Poultry Aid. Then today I noticed one with neck issue has indications of her vent area starting to look irritated, but no feather loss yet. Most poop I see is normal, occasionally find some darker, runnier versions, but haven't witnessed who that is, and it's not much. No blood in stool. Really don't think it's vent gleet - no smelly discharges or build up, no swelling. They are on an organic layer pellet (can't remember the name). Water either has ACV (2-3 tsp/2gal water) or Oxine (1/8tsp/2gal). Occasional use of NutriDrench (during molt, when I thought they had a respiratory issue, when one had bumblefoot). They get dried mealworms, peanuts, sunflower seeds, berries, banana, hanging cabbage, etc for treats (always later in day, to ensure they are getting most food from their feed and nature). When enclosed, they are in a 10x12 run, with access underneath coop. Coop has pine shavings only. Due to excessive water & mud, we've been using straw on floor of run since late fall. This is changed 7-10 days. Again, all are behaving normally, no one appears to be in distress (except me!) Last coop cleaning I used DE on floor before putting down shavings. Also have provided a nice dust bathing bin (large and low) inside run, composed of soil, sand, and DE thoroughly mixed for times when they are either in run all day or there's been snow on ground. They just use is to scratch around in! I know this is long, but wanted to provide as much info as I could. TIA for any advice or suggestions!