2 of 6 chickens walking around with poop on their butts. Is this something bad that I should be treating? I've heard of chickens getting stopped up. These are my first ones.
Some chickens may get soiled vents if they have had some runny droppings, especially in hot weather when drinking a lot of water. In hot weather when flies are out, the danger of not cleaning them off is that they can get flystrike when flies lay maggot larvae. Using a bucket and warm soapy water (in warm weather,) they can easily be washed off. Trimming excess fluff may also help.