Aeroponic Santanaka Peppers/ Root Question

About 1.5 month ago i started some peppers. I placed 3 seeds in every rockwool cube. I p.h the water to 5.5 as listed on the grodon website. Most of the cube's germinated and an average of 2 per cube germinated. I have been using just p.h. water for the first couple weeks because the root development has slowed. about a week ago
I applied the recipe for success starter kit(transplanting stage). Suger daddy and Root 66.
Root development had a very short boost (1.5 days) and has since slowed. My water's PH is 5.9-6.3. I'm am just using sun light in a window seal

The Tap roots are about 1.5 inches long. they are in 1 inch net cups.

I admit i don't have the appropriate. It is set at 15on/45 off.

Any suggestions?
Maybe is should add the BC Boost and BC Grow

Somebody help?

Sounds like it could be lack of light slowing them down. I overwinter chilli plants under cfl`s to increase 6 hours of winter daylight to 16 hours. I have one on a windowsill (no space under the lights) and its dropped most of its leaves and gone dormant

Yeah let them outside most of the day.

....peppers.... sure....
=)