Since you haven’t gotten a response here on the New England forum (perhaps none of the posters is experienced with stag horn ferns), perhaps try posting on the houseplant forum. If you can add a photo of it that shows how it is growing and on what, that may help. There are many things that can make a plant unhappy, including to much or too little water, changes in light level, pests, old broken down growing medium, etc. so the more info you can include in your post, the better.

https://www.houzz.com/discussions/house-plants-forum-dsbr0-bd~t_29929