At first,...I don't have experience with Satanoperca but still I feel to respond to your post.
In nature eartheaters feed on stuff found in the substrate. This can be algea, water insects, shrimp, small fish, plant mater and so on. In my opinion this should be part of their diet in our tanks as well. So I would recommend to feed good qualety cichlid pellets (NLS for example), algea wafers (spirulina) and/or zucchini but also some frozen or live foods like krill, artemis, chopped mussels or cockles. You could use the cichlid pellets as basic food and feed adittional the vegetable/algea foods and 2 to 3 times a week frozen/live foods.
Main reason for "hole in head" (and most other illnesses) are stress, poor qualety foods (mostly lack on vegetable matter = vitamins) and bad water qualety or a combination of mentioned reasons.