I have this suggested though some of the reading I have did that if they do not ingest the rest of the egg goo (not sure what to call it) that this can slow their growth. The chameleons that fall into this catagory do not eat as well right off the bat and seem to just not grow as fast at first. With any animal that has multiple babies or eggs there seems to almost always be a runt. Either one of these could be a possibility.
Is he eating well?
How many and what size feeders?