Help needed with a hen

Hi,

I have a problem with 1 of my ex battery hens, we've had her for a little longer than a year and she was a little older than a year when we got her so she around 2 years, she lives with 10 other chickens, 3 other ex batts, a cockerel and others. Well i was down their checking them out earlier and i saw that she was looking vry run down (there all abit mucky and some are moulting) but she in particular looked quite bad, ratty feathers, muddy, moulting and juist generally looking bad. so i picked her up an decided to check her out, imeadiatly i noticed red skin at her tail, at closer inspection she was bright red all around her tail and bottem, it seems a little dry ,not to much though, and she has some new feathers growing through, i thought it might be mites or lice, but she is the only one like it, and ther were no sighns of any, she isn't itching and aklso i have reactions to might bites so i know whenever they have them.  i doubt it the cockerel because he doesn't go for the exbattery hens, just the 2 brahmas and the orpington.

Does anyone know whats wrong? or how i can fix it? (sorry for the long post)

I don't know about her laying, how would cat food help?

aldi do a box of cat food in small packets, all fish flavour, mine get a packet a week, and it does not last long, just a bit of extra protein, which is what they get from eating feathers.
they also get a tin of sweetcorn, no added salt etc, which does not last long.
if you are concerned about the redness, consider a spray with gentian violet, which will hide the redness, so the others would not be attracted

No worries - I get waylaid a lot these days as well 

thanks all for the advice i shall look into using these techniques