Could water temp. and food availability be the reason that Pumpkinseeds are doing so well and Redears are not?
My guess it food availability. Mollusks (pond and rams horn snails and fingernail clams), that normally provide an alternative for both species when they co-occur with bluegill, dropped out very early. If memory serves, then pumpkinseed better suited for targeting smaller prey that do not require heavy pharyngeal teeth to process. The pumpkinseed also seem more adept at feeding on insects falling on water surface. Would be an effort to measure but redear seem to operate at greater depth than the pumpkinseed.
For fun I might provide rams horn snails of various sizes and see how everyone reacts. I could also check Missouri river and look for a heavier shelled snail species that might be able to persist with both shellcrackers and possibly provide redear with a something they can handle better than pumpkinseeds can. I was very surprised the snails dropped out completely but I do not know what is going on at greater depths (>6').