Not knowing or seeing the animal it's impossible to tell.
The animal could have been extremely small out of the egg and a slower starter which could explain the wait, after that it depends on the prey size and feeding frequency...not every BP hatch at 60/70 grams, not every BP eat a week after they first shed and not every BP eat every 3 to 5 days.
I pay a lot more importance to an animal's look (and by that I mean proportion) then I do it's weight/age.
I hatched a 24 grams BP on 10/30/12 and he ate on his own a week after his first shed (which is 3 weeks after hatching) and he just now passed the 100 gram mark (obviously the preys he was eating had to be VERY small) should he have started eating later he could be smaller than that now.