At his age, not eating all his cecals is pretty normal. Are you feeding an alfalfa-based pellet? That's important for young bunnies. Once he reaches 6 months or so, you should start cutting back on the amount of pellets he gets, and then gradually switch to timothy pellets. If an adult rabbit isn't eating their cecal poos, it usually means they get too many pellets.
It may be good to have a vet do a fecal float to make sure there aren't parasites. That can sometimes cause bunnies to not eat their cecals. In addition, if he's on a wire-bottomed cage, he may not be getting the chance to eat the cecals--they can just fall right through the bars. Just something to think about if you have that kind of cage.
