mouse symptoms

Question
I go to school in Florida, but I have a mouse at home in Massachusetts. I found him quivering in fear in a neighbor's front yard while running my dogs one evening. He is a white mouse, most likely cruelly released by a pet owner or escaped from being snake food, but most definitely not wild. He has been relatively tame, and rarely bites. I found him last summer, and have no idea about his age.

My parents have been caring for him, and have just reported that he has been unusually lethargic (he is usually very active in the wheel and climbs all over the cage) and has watery eyes. Now, since I've been at school he has gotten significantly heavier, and I know they do not feed him the healthiest diet, even though he has a bowl constantly filled with nutricare mouse food.

Do you have any idea what is causing this? Is it old age, or  are my parents the cause for blame? (which is of course what I automatically assumed) I don't think they're up for bringing him to the vet, so I would like to try and have them fix the problem themselves so I can see him again when I come home in two weeks.

Thank you!

Answer
Sorry for the delay in my reply due to my computer breaking! Without taking this mouse to a vet, theres not really much I can help you with. Sick animals need vet care, if your parents dont accept this, maybe its not a good idea to leave animals in their care. Even a small mouse can feel pain and it suffers if it is ill and left untreated. Maybe you can explain this to them. Good luck