Good growth?

After a few weeks of tweaking lights, soil, pots and nutrients I think I have a decent environment for my three feminized white widow plants. Each young'un is surrounded by at least 100 true watts worth of cfls about two inches away. Soil ph is slightly alkaline (about 7.5).
The one plant I'm wondering about germinated in-pot a long three weeks ago and has advanced to about 10 cm in height. Question is, is she where someone her age should be, or is there something I've overlooked that may be holding her back. Any ideas? Thanks...