What’s wrong when a staghorn fern has stopped producing new growth

Q: Our 50-year-old staghorn fern is slowly dying. It is in the same location, in the shade facing north.  We feed it occasionally with Miracle- Gro and a banana peel and spray lightly every few days more when the weather is hot. It has quit producing new growth. I cut the giant root base in half because it was all dead material. Is there anything we can do to save it?
A: Staghorn ferns belong to the group of plants called epiphytes (this group also includes bromeliads and air plants). These