I would not add adoketa because they're a fairly shy, retiring fish that don't like a lot of activity. Mine spend a lot of time hiding. They are in a species tank.
Twelve geos, even with orange heads, is a lot. I'd probably cut that number in half.
G. brasiliensis are not true geos and will hopefully be reclassified into their own genus at some point. They are very aggressive fish and are more like Central Americans in terms of temperament, so I would not mix them with my more peaceful geos.
Satanoperca jurupari are not geos, they have their own genus even though they're often mislabeled. I have always shied away from Satanoperca species because they seem to not tolerate harder water and higher pH very well, so make sure you have suitable conditions for them.
It's odd that the lemons are hiding. Is there too much current? Or it's possible that the severums are trying to eat them and so they stay corralled in a corner for safety. If that's the case, go with larger and deeper-bodied tetras.
If you're looking for a few more cichlids to round out your stock, you could always get a small group of wild angelfish. You could find a pair of keyholes. If you wanted small fish with a big attitude you could add a pair of dwarf pikes like C. regani or C. notophthalmus. If you want another showpiece fish you could try a chocolate cichlid. You could also do a single acara of some type, or some Krobia, or a nice Bujurquina species which are mouthbrooders. They sometimes come in a nice yellow color. There are lots of options for peaceful cichlids in the medium size range.
