[treacleminer]

I took advantage of not having changed the timer yet on the chicken house this morning to grab my Light Sussex (Gertie) and give her yet another wash & dry.

She tends to a dirty bum - and always has had hence the name! - Has anyone any suggestions why that might be?
They've all been wormed (flubenvet), has plenty of grass, eats mainly layers pellets with a small handful of corn of an evening. 

She is definately better when I block the nest boxes so she can't roost there.  My only thought has been that she's quite a healthy size and is just too lazy to preen properly?
Is this likely or is something I'm missing?
Any suggestions gratefully received
Janet