Or it could be over watered, slightly different nute or soil build up. Or it could not be getting the same par levels as the other plants, could have had some stress. Lots of reasons. But could also just be a dodgy seed, can't change nature.
Il say its a defect in the seed or she turning hermie on you by the looks cause auto amnesia is sativa x rudaris so should be bigger aswell.
But theirs always one