Nico, my two and a half year old rat has been only eating very small bits of food that are soft, such as oatmeal or tiny pieces of pasta. (Like the size of one of his paws) He wont accept oxbow adult rat food pellets, even if they're in small chunks. He also won't accept any hard food, or simply anything in large quantities. His feces are like half the normal size, is that because he's not eating? What's wrong with him?