So I have three rats. Two are brothers and they are a little over two years old. One of the brothers has been slowly declining in health. He's always been a picky eater so he's always been the skinniest of the two but now he is very, very underweight. He barely eats. He won't eat solid food so I've been preparing him baby food. I do a bowl of oatmeal with fruit, pureed vegetables, and pureed chicken. I'll mix some crushed up blocks with the oatmeal too. He eats a little bit but not enough. I bought some Nutri-cal for kittens today to see if that will help him gain weight. His eyes and fur are dull. He has no energy. Occasionally he'll start breathing with his mouth open and making a clicking noise. It's only when he exerts himself. He is still drinking normally. He just stays in his hammock all day. He used to be house trained but now he has consistent accidents outside the cage. I was wondering if this is just old age setting in or is he sick? He's been declining for a couple months now but its been very slow. He seems to have leveled out now. Nothing has gotten worse or better. The only thing he seems to be doing better is grooming himself. Although I can't tell if it's him doing it our the other boys. I feel like if he was sick it would've escalated a lot quicker seeing as how rats immune systems aren't the best but his brother is the same age and he's completely fine. My university has a vet school and I study in the same department as them so I'm thinking about talking to one of them about it or seeing if they know a professor who could give me some insight. Sorry about how long this is. I don't want to put him down if this is something that can get better but if it's not then I want to do the humane thing.