sick butted chick

[one wet hen]

i have a three week old copper maran that is taking corrid(she was the only one sick but "every ones" taking meds) the bigger ones are always picking on her....today i pick her up to look at her her side of her butt looked really raw like her feathers were rubbed on sandpaper...i washed it with warm water and put some arnica ointment on it ect can anyone tell me if it looks "picked" on or if she sick or ?...

 

[one wet hen]

file:///Users/michaelperron/Pictures/iPhoto Library/Originals/2011/Apr 12, 2011/IMG_0614.JPG

 

[one wet hen]

hopefully it loads this time

.....this after i have washed it and put ointment on it...