Dirty chicken butt

[free range by day]

What would be the cause of one hen out of 37, to have a dirty butt and not laying anymore? Maybe one a week if that. ( she’s my only cream legbar and my only blue layer which is why I know she’s not laying)
She’s had this dirty poopy butt for a few weeks now and she’s the only one.She is eating, drinking, and acting completely normal. Just dirty butt and not laying

 

[RedHillChicken]

What would be the cause of one hen out of 37, to have a dirty butt and not laying anymore? Maybe one a week if that. ( she’s my only cream legbar and my only blue layer which is why I know she’s not laying)
She’s had this dirty poopy butt for a few weeks now and she’s the only one.She is eating, drinking, and acting completely normal. Just dirty butt and not laying

Is this a discharge, or just poop stuck on her butt feathers? Color? No abnormal symptoms?

 

[free range by day]

Is this a discharge, or just poop stuck on her butt feathers? Color? No abnormal symptoms?

More than poop stuck on her feathers. Looks wet (almost diarrhea looking) dirty. Other than this she is acting totally normal.