I have a baby nigerian that I think has a problem. He was born December 1st and recently weaned. He had been doing great but lately it doesn't seem like he is growing, except his stomach which feels very tight. Also he seems weak like he is having trouble getting up and when he does he won't walk around. I looked at his eyes and they look fine, no sign of worms. His fecals are normal as well. What could be the problem?