Is my chook moulting?

I am quite new to this chicken keeping lark and I love it.  So far I've had a trouble free time with them.  I have 5 girls (since October 2008) and they've been in good health.  Today, though, I noticed that one of them had a patch on her breast that was devoid of feathers and the skin looked pink.  Is this moulting, or does she have a problem?  I've noticed a bit of bickering going on, though didn't think it was any different from the usual.  None of them has moulted before.  I feed them LP (with a bit of mixed corn at this time of the year) and some chicken spice in their feed and at the moment a bit of vitamin supplement in their water as I've had a few delicate shells.  I'm only getting on average 4 eggs a day but don't know who's not laying. 

Since I noticed the bare patch today we have separated her from the rest of the group and can try and put her in a separate place overnight.  is this the best thing to do?  Other than that she seems ok.  She ruffles her feathers a bit more than usual.  her comb I think looks ok and she continues to be as noisy as usual (she's the noisy one of the tribe).  is there anything else I should be looking for?  We caught her to look more closely and she didn't like it - does this mean that she was sore when I touched her bare batch?  The bare batch is not huge but noticeable - about 1 square inch.

Any advice would be gratefully received!  Many thanks in advance
Julia

thank you!  Any other comments are gratefully received.  I'll pop along to the shop tomorrow for purple spray.  Better go and reintroduce them again now before it gets dark. Do you think it safe to let her stay in with the others tonight?

Julia

Thank you!  Are lice likely at this time of the year?

What breed is your chicken? If she's a pure breed I'd definitely say she's preparing to go broody.  Spending a lot of time on the nestbox and puffing out her feathers when you try to move her and grumbling in a bad tempered sort of way are dead give aways for broodiness.  I don't think there's any need to separate her or to be too concerned.
HF

just to add a bit more info... I popped down to the animal feeds place and on advice bought some vetinary antiseptic gel.  Just applied to my girl.  The bar patch is quite pink, not broken, but runs from her neck down her breast and belly.   A friend looked at it earlier and said it could be that she's been rubbing against something?  She didn't flinch or get distressed when I applied the gel.  I haven't noticed her getting broody or anything.  She's perhaps a little quieter than usual and the others dont' seem to be any different with her.

I hope I'm doing the right thing ....
Julia

just to add a bit more info... I popped down to the animal feeds place and on advice bought some vetinary antiseptic gel.  Just applied to my girl.  The bar patch is quite pink, not broken, but runs from her neck down her breast and belly.   A friend looked at it earlier and said it could be that she's been rubbing against something?  She didn't flinch or get distressed when I applied the gel.  I haven't noticed her getting broody or anything.  She's perhaps a little quieter than usual and the others dont' seem to be any different with her.

I hope I'm doing the right thing ....
Julia

Usually hybrids don't go broody to any extent though it's not unknown.  The only other thing you might check for is Breast Blister which is usually associated with broilers and wet litter.  Make sure she has dry clean litter.  Breast blister, as its name suggests, is a blister on the keel of the hen which contains fluid as a result of a bacterial infection.  There might be info in the stickies area or google it for more info.  If it is, it isn't usually fatal and providing more sterile litter and eliminating any sharp edges which might be irritating or abraiding her keel is the usual treatment.  However it doesn't sound like this and I'd still opt for broodiness (the hen plucks its own feathers preparatory to sitting on eggs).
HF