As latewood said, all seeds are different. Different strains, different genetics. I started a few seeds some weeks ago, all at the same time, and one is way bigger than the other. I had to make levels for them so they all stay at the same height. They are just diff. strains, so some grow faster than others.

I wouldn't worry so much about the stretching now. Just try and keep your lights as close to the plant as you can get without damaging the tops. When you transplant into bigger containers, once they get bigger, you can add more dirt to the bottom of the plant and cover the stretched stem up. Good luck.