Ill Gerbil and perhaps a depressed one?

Question
We have 3 male gerbils approxiametly 2 years old. We separated 1 off from the other 2, about 2 months ago and recently he has been eating less than normal. He will eat sunflower seeds from your hand when he's out.
Also one of the other 2 has had green poo. What should we do?  

Answer
It sounds like one is missing it's friends but it will adjust soon enough. As long as he's eating he should be fine and will adjust to being alone soon. The green poo is generally because something is not agreeing with his stomach. Have you changed his diet recently?? I would really consider taking him to a vet just to see if he needs some antibiotics for him. I would bring in all 3 gerbils to get looked at just because if you bring one and something is wrong chances are that the other two may get something as well.