Not sure that I totally understand, but I always remove the seedling from the humidity dome after it breaks the surface of the rockwool cube. If not they will stretch.
The cube should be moist but not soaking wet (damping off happens), and don't try to squeeze out the excess water. Rockwool will hold air pockets unless you defeat the purpose by squeezing them. Roots need oxygen.
said above, all seeds are not created equal.
Here is a great site that I always recommend for new growers..veterans find it helpful too!
Growing weed can be easy, though some marijuana grow tutorials make it seem like you need a degree in horticulture. Learn how to plant a seed & start growing with as little time and effort as possible, or read our advanced tutorials for monstrous yields!