No, yearlings are often about 2'- don't believe everything you read- some ppl power-feed their snakes too. Yours looks fine & healthy! Corn snakes start off about 8-10" long when they hatch, & they can only eat pinkies for months, so they don't grow very fast normally. Even then, their food goes for energy (activity), not just growth. Commercial breeders do tend to feed on the light side, but either way, once snakes start eating bigger prey, they grow plenty fast.