I had to rush Lizzie hen to the emergency vet today after finding her in a blood bath. The others had pecked her vent, it looks as if they have gone at her with a razor blade.
I did everything I could think of for her before we set off (bathed her wounds with diluted veterinary iodine solution and gave her some sugared water orally to reduce shock) the vet was happy with her treatment and bathed her wounds a little more, baytril prescribed to take home for her. She is very poorly but still here, please keep your fingers crossed. I will update on her soon.