I would cut back on the mice. If its Four years old, and depending on whether its a male or a female, only needs to eat once every ten to fourteen days. Change things up with a trip to the store once every couple of weeks and get some nightcrawlers or crickets, or some healthy looking fish (avoid the cheap feeder fish tanks) Cut the mice back to once a month.

If you change your bedding every two weeks, then you should consider checking out the conditions of your water and also whether or not the coco fiber is getting soggy.