Adding onto this as well... (though deb posted as well. Nice post!)
Weight isn't as important as you knowing your snake is healthy and in good body condition. Which is why mine are on the small side by weight standards for thier age. They are otherwise in good body condition. Not thin or malnourished.
I've only been monitoring weights on my snakes this year because they all have different issues where having a good weight helps.
Snakes will all grow at different rates and such, but as long as you have a good body condition, all is well. If your snake is visually thin, then that needs to be corrected.