Ya brother that is the strain the indica vs the sativa effect. The fact that you have gone from the tiny girls in first week to now is great, the growth is dead on in my opinion. The indica grows slow and has tighter internode gaps then say the sativa would. If your looking for a bigger stretch in growth from these girls increase the height of this light and the difference in temperature from day and nightime , if you get a 15-12 degree difference in temperature then it can cause a stretch but not very significant right now .There is the fact that you can just run the vegetative cycle for longer till you get that desired height or run some sativas for the next grow.. cheers

Yes you are. It has a lot to do with the strain and genes. Indicas produce short compact plants with big fat fan leaves. Which u have. To help them stretch more is to raise grow light. Another trick is to have a 10 or 15 degree difference between night and day temps. That tends to make plants stretch. But next run if u want more internode spacing I would go with a hybrid or sativa strain.