You might just get away with these, but I would prefer to keep all of those species in a considerably larger tank.single electric blue acara could give a pop of color.
a marbled headstander or 2?
anostomus ternetzi?
Angel fish?
A pair of Laetacaras would be good - L. araguaiae, dorsigera or curviceps. A bit bigger than most Apistogrammas, but manageable in that tank size, they tend to stay together as a pair (with occasional not too serious arguments), unlike most Apistogrammas.