How is this mouse?

http://img198.imageshack.us/img198/760/p1030099g.jpg
She's only 8 grams. Her tail looks bony. She moves really slow. They have food and water. The others look healthy.

thats a slow walker, basically the runt. my friends dad i told u about earlier feeds those to his king snake and nothings wrong with him. if u leave him alone he'll die cause the other mice will take his food and wont be allowed on the wheel if u have one of those for excercise. hes not sick just small, it happens in most litters but if u get him checked out and he is, then its safe to assume the rest are too. as u know im not an expert but this is what i know from a breeder