The Keys corns do tend to run a little smaller, Pugs. But even within a morph size is still variable from snake to snake. I would not expect a keys snake to grow as big as some of the Okeetee. Knowing the size of the parents helps.
Feeding a baby snake a pinky once a week is not starving it. It won't grow as fast as a baby fed every 4 days, but unless you are in a hurry to grow up a snake there is really no absolute need to feed them more often. If it's a bigger snake then it needs to be on something bigger than pinkies but the weekly schedule is fine.
I am mainly posting because of the "once a week" thing, I feel this needs to be defended for some reason. I feed all my snakes on a once a week schedule including babies, they might not grow as fast as other people's babies but I have never had a customer complain that the snake I sold was undersized, either.
I also don't expect them to be a certain size by a certain age, I just keep an eye on their overall condition - if a snake is shaped like a "loaf of bread" it is healthy. Some of them just grow faster than others. A chart is a handy tool but it does not replace your eyes and hands as you look at or feel the snake. Is it strong, alert, active? Forget about how many grams it should be by that age, that is a number someone put out there because they think it's right- but the bottom line is that condition is what;s important, not size.
I was one of the people who felt a great deal of resistance to that munson plan from the start and even Roy Munson did eventually revise it because some of his own snakes became a bit overweight on the first version, There is a fine line between wanting your snake to grow and power feeding and it is a lot harder to take the hips off the overwieght snake once it reaches that point, than it is to prevent it by not overfeeding in the first place.