chook problem

[Twinkle]

I've 3 hens (2 RIR and a Black Rock hybrid) who free range and are fed layers pellets. The hybrid doesn't lay any more as she's an old lady, but the 2 Rhodies are only 2 years old and we're lucky to get 1 egg every other day.
I've noticed recently that they all have permanently pooey bum-feathers instead of the rather fetching "fluffy bums" they used to sport.
They do dust bath daily, but I have to keep catching them and washing them (which they don't like)

Any suggestions ??

No signs of mite, and I'm about to worm them this week... Poos look normal, well the ones I've seen/trodden in are...

[RichmondHens]

Probably parasites of some sort. Worm them asap with Flubenvet which will kill all worms. Also give them a thorough louse powdering. Chickens sometimes poo down themselves deliberately to try and get rid of lice.

If they are active, laying and eating well there won't be much else wrong with them. If they had coccidiosis (another cause of pooey bums) they would be standing around hunched with ruffled feathers and not looking very well.