Q.You Show Staghorn With Brown Under Side, What Is Problem And How To Correct, Please?
Many thanks for your help and answer ☺️

Certified GKH Gardening Expert
I didn't see a photo with brown underside unless you mean the one with brown leaves. Basal leaves start green and change to brown. They supply nutrients and should not be removed.
Spores on the underside of leaves turn brown and can be collected for propagating.
https://www.gardeningknowhow.com/ornamental/foliage/staghorn-fern/gathering-staghorn-fern-spores.htm
https://www.gardeningknowhow.com/ornamental/foliage/staghorn-fern/cleaning-staghorn-ferns.htm
https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/staghorn-fern.html