You could try limiting the pellets a little bit, not cutting them out completely. Hay is important, so it’s good if he eats extra of that. A hay-only diet is often recommended for adult rabbits that have a soft cecal/mushy poop-problem, but your bun isn’t an adult.
It’s common for babies to leave a few extra cecals around. That’s normal. Bunnies rarely like to eat the cecals that have fallen to the floor. He’d have to be really plump to not be able to reach down to eat his ceacls when they come out, seeing that he’s a young bunny (elderly bunnies can get arthric/less agile and combined with a bit of over weight, that can make them unable to reach their cecals.) He could perhaps eat the cecaols he needs when you’re not looking?
Baby buns’ tummies are not fully equipped microbial-wise, a sturdy gut microbiota takes some time to establish. Hay is the best thing for normalizing a bun’s gut.
If he gets ample, runny diarrhea, of course rush him to a vet.