Stained vent feathers

[albodean]

Hi All,

Wasn't sure where to post this as it's not an emergency, please move if needed.

One of my Light Sussex pullets has poo stains below her vent, not sure how better to word it I'm afraid! I have put a picture below. Both of my other pullets are spotless in this area. Is it normal or do I need to do something?

 

[Pork Pie]

Its certainly normal for some of my flock.