Depluming mites? Pecking?

[CedarRanch]

I have a flock of 19 hens, 2 roosters, and 6 12 week old chicks. Noticed some missing back feathers about a month ago on 2 of my hens. I figured they were being overbred. I ordered saddles and left it alone. Now about 7-8 hens have the same loss of feathers in their back. There are feathers all over my coop floor and outside of the coop around where they hang out the most. I am not seeing any pecking/plucking but I'm obviously not watching all day long. My roosters don't seem to have any missing feathers, nor do my guineas, or my 12 week old chicks. We did recently have a significant snow, where they mostly refused to leave the coop for about 2ish weeks. One of my very old, and frankly near death, hens have wispy feathers. She is going through a very hard molt at the same time. I truly don't suspect she will make it through the year. This is just throwing me for a loop. I want to assume its not mites because they'd all have them right? But I can't seem to count it out because that one chicken has what looks like damaged feathers and not just plucked feathers. All of the feather loss is on their lower back. None have feather loss on sides, head/neck, bellies, or bottoms except that one wellsummer. If it is mites, what would be the treatment? It is still cold here, I don't think I can do a Elector soak without potentially making them sick. I've already ordered a full plume feed and they're leaving the coop now so if it is plucking/pecking hopefully those will help.

 

[sourland]

Looks like feather pecking/plucking to me. Generally it's the birds in perfect feather that are the culprits. If all appear pecked, it may very well be the Guinea fowl.