Everlasting moult

Hi all, three of my girls have been moulting for almost a year well there abouts, they all have bare bottoms, I thought because we have had a really bad winter that this was the reason, they are still laying and are in good health, they were wormed about a month ago, so i'm really puzzeled, they do look scruffy, any ideas?

If your hens have been feather plucking when the new quills were coming through they will have bare bottoms until the next molt.  I had a Black Rock that had a bald bottom for around 8 months.  She is full clothed again now and a picture of beauty.    

Hi, they don@t have lice i have checked them, my light sussex is fully feathered and so is my bluebell and speckeldy, it just seems to be my warrens and my blackrock....... strange.some of them roost ans some sleep in the nest box, i try to keep them as clean as possible. perhaps i need to be patient, is there a tonic or something to help them while they moult?
Thankyou for the replies

Like my bald-bottomed girls??

Anastasia was picked on from the beginning - she is permanently bald!
The others have more recently become scruffy

But they seem happy!

I do!
I love my scruffy girls