Hens with poop on their butt

Hi guys, I have a 5 chickens, 2 of which are the same breed and keep getting lots of poop stuck on their butt feathers.

I’ve washed them both multiple times and it is reoccurring no matter how often I clean them. Is this specific to their breed since none of my other chickens have this problem?

They are Sussex hens I think, not sure their age cuz they are rescues but I’ve had them for 3 years.