My laying hens have matted wet butts!

[gr8expectations]

Two out of my six hens are big enough to lay. Our wyandotte had a matted wet butt yesterday, though its back to fluffy today. Our sex-link has a matted wet butt today and may have lost a little weight recently. We're pretty new to chickens (3 months) and have no idea what to do, but they have been healthy happy birds up till now. Please advise.

 

[chookchick]

What do their poos look like? Do they have diarrhea? What is their bedding and is it nice and clean? Has their behavior changed at all? I take it they are not laying yet..?