Molting?

[Denise1015]

Hello... posting my concern again with photos and video. Have 8 hens and a roo. 2 hens are from same clutch. They are about 12 months. Both began molting ( I think) Their back feathers near tail are all down with white feathers all over their barn daily. The one sister walks slow, is lathargic. Both have dirty butts. They get probiotics (started a few days ago). The one I am questioning spent time in crate so I could monitor. No respiratory issues. They were all treated for worms a few months ago. She eats. She follows the flock. She will not jump up
On roost at night. Please take notice of feathers on back by tail feathers. Both sisters are not laying. In the video she is on left, sister lower right. Any input appreciated!

 

[coach723]

Loss of feathers in that area is usually caused by a rooster mounting. Do you see pin feathers coming in anywhere? That is usually the indication of molt. How old is your roo?
Depending on age and personalities, 8 hens may be enough for one roo, or it may not. When there are not enough hens they get over mated and start to look beat up. The hens in question may also just be more submissive and get more attention.
Depending on the parasite load in your particular environment, worms can be a recurring problem, every flock is different. If they are acting sick with runny droppings then I would recommend getting a fecal done to see if parasites are an issue.
I did see in a previous thread that you had a suspected respiratory issue previously in your flock, so depending on what it was/is it also could recur periodically, symptoms often come back during times of stress.
At 12 months they are young for a reproductive problem, but it can still happen. Are crops empty in the morning before eating or drinking? Feel their abdomens, below the vent, between the legs, to see if they feel bloated at all.
If you posted a video, it's not showing.

 

[Myrshine]

Do you have a rooster? It almost looks like over mating feather loss from a rooster. If you don’t have a rooster, they could be picking in each other or you may be dealing with lice or mites. Check them for lice and mites