I do not know exatly what your
pH is at but Geo should be in different pH water from Rift Valeey African Cichlids. Although fish can tolerate/adapt to wider range of pH than specified/known, this
maybe classic symptoms where extreme condition when exposed for prolonged time (Chronic effect than acute effect of extreme pH), eventually will weaken fish to a point where it can not defend itself ot mates see/notice such weakening behavior of fish. COMPETITION!.
What is present pH of tank? Is it possible to
DIY contraption where it can be isolated in same tank if separate tank is not an option at this point?
Hope this helped!