Newbie outdoor problem....

Hi I have 5 plants of utopia haze, they have sprouted 2 weeks ago. My problem is that one of them is not growing it is still 2 inches tall and has only two little leaves, while my other plants are 7 inches tall and are in great condition, full of new leaves. What can the problem be? has this issue ever happened to anyone?

thanks

I had a similar problem with a sprout 2weeks old, same problem didnt grow fast enough, so i pulled it out of the dirt and the seed case was stuck tight around the root slowing the growth. it ended up dieing so basically a weak plant with strong seed case.