My DWC (Deep water culture) at home

The begining of week 2: I had added 6 ml of Hydro A & 6 ml of Hydro B to my bucket. It increses total PPM from 384 to 504. Also I droped down Ph of solution from 6.6 to 5.85. The plant in DWC looks twice bigger than a plant in a plastic cup Day 12. It's looking like stem of my girl did't growing at all. Maybe a few mm in four days. Any advises on that? Maybe it happening beacouse of the light stress, a week ago distance was about 35 cm, then I moved up the lamp to 85 cm, today encreased the distance to 106 cm. The leafs looks big and healthy, but stem looks a bit thin, I think. The roots start showing up. Today I've seen them first time.