We found one of our young hens dead this morning without a mark on her. She was fine yesterday, active and feeding. 3 of the other 4 hens I noticed today are sneezing/coughing and have runny noses. Is there something I can treat them with as I am now really worried that she died of something contagious and we don't want the rest of our ladies to die too!

If I am being silly and hens just fall off their perch sometimes please do not be afraid to tell me!!

Many thanks if you can help!