Lookin' around...
Hey Y'all, I had to comment. Variable growth !! Variable genetics !!
Wild growth patterns are different than captive growth patterns !
But not always, but most people think they have to stuff their snakes to get a particulaly desired growth rate

Snakes that live in the north may only be active 5-6 months a year ~ !
So they don't grow as fast as yours.
I have heard of some snakes reaching 5 feet in their first year
and with cornsnakes, some people get them to 3 feet. But remember that might along with excessive breeding, shorten their lifespans.
But if they are going to live to be 30 and you breed them 5 or 8 times, I doubt its going to shorten it much.
So if you are just keeping pets.. I wouldn't worry too much about its growth but if you want to speed it up, give it some larger meals, increase the temperature a little and you will see a change.
Most of these snakes can eat meals bigger than we feed them but on the other hand, small meals more frequently is the better route to go according to who I have talked to and read...
What a neat neat forum this is.
Pardon my excitement but I had to contribute something ...
so hopefully there is something in there that helps.