Gotcha.
I feed Equine Senior and grass hay to all ours (I just feed way less to the pony) They don't have needs near as demanding as yours. I mix the Senior pellets with a little sweet COB when I think they don't need it that rich. Right now I'm mixing their feed two bags senior to one bag sweet 12.
That's what I'm trying to end :) mixing feeds. It sounds like what you're doing works well for your guys though.