Why are not all the same

Not much to go by but here is my best shot. Yes they may have been seeds from the same package. Each seed is its own individual with a specific DNA. So yes they may all be the same strain but not every seed will perform the same. It’s like asking why you and your siblings aren’t the same. You all came from the same parents, right?! But each of you are your own individual. Well it’s the same thing with seeds.

Different phenos might grow at different hights, a net or LST in veg could help keep the same hight