There's a degree of randomness which could have been at fault. There is a 10% chance for each child to be one size larger or smaller than the average size of the parents. So you get there eventually if you go through enough generations.
But if you go through too many generations there is a chance you lose the red or yellow genes entirely, so you'd have to reset.
I was going to add some other genes which would change the carrot shape or make the carrots rabbit proof (there were going to be rabbits that occasionally ate the carrots). But there were a bunch of aspects to game design that I hadn't considered before so I ran out of time haha
