I went back to see what nutes your using, the 15-30-15 is more of a flowering mix. You can buy nutes on-line that are specific for cannabis and from my experience is worth the cost. I started out with vegetable ferts and now that I started using the cannabis nutes, there is no camparison, the cannabis nutes are way better. I use Advanced Nutrients Jungle Juice 2-part and really like the nutes. Other brands are available that I'm sure are just as good. Look around as to what others on this forum are using.
For vegetative growth, you need a higher nitrogen fert like 30-15-15. After your girls stop stretching, then switch to the higher phos fert like 15-30-15. These vegetable ferts do work, but with limited success compared to the cannabis nutes. Watch your pH, most of these vegetable ferts are not produced with the purest of materials and can build up rather quickly.