Staghorn fern not thriving - edges of several fronds have definitely been chewed but only thing visible are ocassional scale which I physically remove. Obviously cannot see into layered basal fronds. There is some sticky substance that seems to drop from the edges, probably plant trying to defend itself. Some fronds also seem to be cracking. Thought might be some pests in planting medium, so have re-planted in new orchid bark in hanging moss basket. Have also worked a little systemic insecticide into the dirt. Tried checking with a flashlight before sleeping but haven't seen anything, so must be late at night??? Plant still not happy! Am not sure what else to try - plant is very sentimental and would very much like to get it back to it's formerly robust self!