a distant observer sees them all redshifted. But that says nothing about how the ships see each other.
Consider: Even in the case of Captain #50 viewing the USS #1 crossing the event horizon, Captain #50 receiving the photon will also be on the event horizon when that happens. So the photon travels **along** the event horizon between a source and a destination that are both **on** the event horizon and that both have the same rate of time-dilation w.r.t. a distant observer. So I'm not seeing how there's red-shift.