Messy feathers + Other questions

Firstly hello!

I've only been keeping chickens about 6 months, and so would like some advice on them.

After having 2 out of 3 chickens not survive over winter (for different reasons, one had can cancer of the bowels/intestines, the other just as far as I could work out couldn't deal with the cold.) so I recently got 2 more.

The three chickens I have now are all Neras, the two new ones are pullets/on the edge of starting to lay, whereas the one that survived winter is laying regularly.

However they seem to different degrees have messy feathers near their vents. I don't know why and as I don't want to lose any of them I would like some advice on why they are messy and how to stop it if possible. 

Additional info about the hens that may or not be important:
- The older one is still laying regularly.
- They all seem happy and active, none look hunched up I've looked for mites and i'm sure they are mite free. (I plan on re powdering/treating their house just to be sure)
- They have layer's pellets as their diet with anything they dig up/eat in the garden (also they will occasionally get vegetable scraps.)

Thanks in advance!

:o How did I miss the whole FAQ section *facepalm*

Thanks for the suggestion, overall the chicken droppings appear the normal white and grey type with the occasional yellowy one which according to the faq thread is normal.

I've given the hens Verm-x worming stuff a fortnight ago, however I'm a tiny bit unsure whether it is any good so I may use the Flubenvet wormer just in case.

Although I'm still unsure as to the messy feathers.

Hi .. new to all this too , but mine has a messy bottom partly due to her very fluffy 'knickers' but also she doesn't roost on the roosting bars and instead prefers to sit in her nest box where she also poo's away til her hearts content and sits in it .. maybe thats what yours are doing?

!! The two new girls are still just pullets and I've opened to coop to them sitting in the nest box at night sometimes. (My older girl roosts on the roost) I do hope this is right.

All the 5 ex-batts that we got (2 prev owners since their battery days) sleep in the nest boxes so sleep in poo - several have mucky bum feathers but seem quite happy otherwise.

I'm planning to block off the boxes overnight when they're more settled and the weather is milder, but they look so cosy cuddled up together or in individual cubicles!

Thank you for all your advice! 

I will give them a wash this weekend, I will also give start them on the Flubenvet.

Hopefully last question:

With the flubenvet I've been learning from my mistakes and browsing the forums, buT i just want to make sure I've got the dosing right.

For 3 chickens with flubenvet 1%, I can grab a 'pinch' of the wormer and add it to a food they'll like and eat up, once a day for 7 days?

Thanks again