Oh, most of my spiders are great eaters, but I get poor starters/poor feeders every once in a while, among the hatchlings. I think it's less common in them than in some other morphs. Then too, it may be lineage.
I think it's important to selectively breed animals with robust appetites. If you have a poor starter that you just have to keep, be sure to pair only with good eaters.
We are responsible for what captive ball pythons become. Virtually all of these traits (feeding response, appetite, adult size, temperament) may be heritable, so it is best to assume they all are.