Duck not right

[cumminsgal827]

Ok so my ten week old duck has not been pooping normal. It is runny and green. Its not always like that but it has me concerned. She is very active, eatting and drinking is normal also. When it is not runny it is usally smaller then normal. Her bother died Monday, I don't know if that could have her stressed out or if thats a sign she is sick. She is with our chickens and what I have observed they all get alone just fine. She's very active and is always moving. Also she has been eating the same food as the chicks since I have got them, never had a problem until now.

Any suggestions?