That is really interesting. I've got a small 20'x25' grow-out pond where I recently put about 75 RES about 1-2 inches. I also put in about 350 FHMs. I just noticed something similar in the last couple of evenings. The RES are not big enough to eat the FHMs.
I've been feeding coarsely ground fish pellets that have been run though an old food processor. When I throw it in the water there is a FHM feeding frenzy. But, the RES are also eating it. During feeding, the FHMs mostly stay in the middle of the pond. The RES come to the edge of the pond to feed, on the surface, as the feed slowly sinks, and off the bottom.
This is also the first time I've ever has RES taking food.
