Feather loss in 3/4 of flock. Help. Thoughts?

For warning... Sorry if this is a long post, just wanna get all the details out...

Hi I have 7 hens. I live in northern MN and I am trying to figure out what is causing feather loss in 5 of my hens. One is in really bad shape, feather condition wise. The others the feather loss is just located to butt. But not the vent, the area under the vent. I will include pictures too. The one who is really bad, I noticed she started losing tail feathers about 3 months ago, real causal, nothing too dramatic. However in the last month she is practically naked on the back side. I have been monitoring all of them daily for about a week now. I am not sure it is a molt though. None of them seem to have pin/blood feathers. But I have also never experienced a molt before either. There skin is smooth and naked. Red at times too, paler others. All the hens are about 9 months old. I have not gone out at night to check for mites/lice yet. But that is on my agenda tonight! There doesn't look to be bite marks or swelling around any of my hens vents though. And the feathers they do have seem, well I have not noticed lice. But again this is my first time experiencing this.

Again the one who is worst off, she is my biggest, and on the top of the pecking order. She doesn't appear to be getting pecked at by the other hens. She doesn't take **** from nobody! Haha. But with monitoring her every day for about a week now, well this morning her neck looks like she lost a bunch of feathers over night! Additionally she has lots of thin patches of feathers. on her legs and under wings. It also appears the hens with feather loss are also having feather damage. They seem to be breaking off mid feather. Also what I think is feather growth, but possibly infection, some of the shafts look bloody, almost like a black head on a person (pictures below).

All the hens appear to be eating and drinking normally. Droppings look fine, have been inspecting the poop shelf and don't see any obvious signs of bugs/worms. Laying has been interment due to winter, but I also have a red heat bulb.

About 3 weeks ago I did a full clean out off the coop and adding new shavings. But I also added a tub of playground sand and mixed it with ash from my fire place (I read on the forum you could do that as a dust bath, several people recommended it). However after taking with my local feed store they wondered if I didn't accidentally make lye by adding to much wood ash. So it may have been dissolving their feathers! So I did a full clean again on Wednesday. Took out all the sand and bedding and put in two fresh bags of pine shavings. But again my big on is still getting worse! I am also offering black sunflower seeds in the morning.

I know they are not broody, they spend all day moving about, I have one who is currently and her feather loss is localized to normal broody spots, doesn't seem to be affected like the other girls are. So my questions are has anyone seen this before? This type of feather loss? If it is molting, can their skin look naked for a few weeks, with no pin feathers? What can I do to help them! Its only January, winter is still here for several months. I will check for mites/lice tonight and get back.

Thanks for reading and offering thoughts and advice.

Worst chicken as far as feather loss

Another hen with feather loss

Another view of my worst.

Bad picture of feathers just above vent.

Patchy neck, new as of this am.

New feather growth or something else?

Another hen with feather loss

Is this new feather growth or something bad?

What are these feathers on her? Normal? A few of them have them. She has bare skin between the fluffy patch.

Neck picture. Noticed it as of last night, as her neck looked patchy this am.

Bloody base to a few of the feathers on her neck.

UPDATE: I found lice on one of my hens.... Super. Looking into treatment options now.

I would suspect that this is from feather picking, not the lice. Feather picking can become a habit, and may result from boredom, over crowding before they are getting out to roam around, or from a lack of protein in the diet. What percentage of protein is in your layer feed? I would increase it for a bit with flock raiser feed or some chopped egg. For the lice use some Permethrin 5% spray or garden dust. The spray is more price effective, and can also be used ro treat the coop. It may need to be applied at 7 day intervals until lice and eggs are gone. For the bare spots on the hens, I have had food luck with BluKote, a blue dying spray that can stain your handw and clothes, but hides the red spots until feathers grow in. Your birds have some pin feathers growing in, and those can be very tempting for the birds to eat. Apply the BluKote every 3 days or as needed.