The dreaded Malawi bloat happens when a fish gets to much protien than it's body can handle. This not seen in all African cichlids, mainly the herbevorus cichlids, mbuna, tropheus, gobies. If your fish are not veggie lovers, then you've nothing to worry about.
If they are, then you still don't have anything to worry about. Like what's already been said, a single pellet isn't going to hurt them. It's when they are feed an improper diet for prolonged periods that it starts to harm them.
I've never heard of a fish getting HTH from too much protien