[Pepperpincushion]

I have six hens and they were living happily together for several months. Then a few weeks ago they started picking on one of them and pecking at her until they drew blood.
I have temporarily solved the issue by shutting her off in the nest box at night with a piece of hardboard so that they can't get to her - they are free range so she is OK when they are out during the day.
It's a pain though - the others can't get into the nest box to lay in the morning so they lay in the coup and the eggs are all mucky - or else they go off and lay randomly in the garden now and we keep finding little nests of eggs in bushes.
Is there anything I can do to help integrate them again?

[kegs]

If there are any red/blooming patches then give her a spray with gentian violet antiseptic spray.  Have you checked her for lice too?  It might be an idea to treat her anyway (I use frontline) just in case.  Would it work to change the piece of hardboard for dark sacking material?  You could pin this up so that it hangs down, she might stay in there out of the way but the others would be able to swap with her when they want to lay in the mornings.  You can also buy anti pecking sprays but I don't know how effective they are. 

[Pepperpincushion]

Yes, I am using gentian violet when she needs it. I looked at the antipecking spray today but as you say I wasn't sure how much good it would be.
I think the trouble with changing the board for cloth is that once she came out - or they went in - then until they were let out they would still all be in close proximity and likely to start getting at her.
The frontline is a thought though - it had crossed my mind, but I couldn't see anything on her. I might go and treat her anyway then.

[Sassy]

Usually the bullying occurs when they are out during the day as at night they are pretty much comatose. If you can identify a ring leader in the bullying it is usually better to remove them for a week or so and then reintroduce them as they go back in bottom of the pecking order.

[Pepperpincushion]

Unfortunately we've seen most of the others pecking at her - it seems they just all see her as the vulnerable one. They are actually fine in the day though as if one has a little go at her she just moves away and none of them can be bothered to chase her - there's plenty enough space in the garden for them all. The attacks only happened when they were left together at night and they woke up in the morning ie before they had been let out.