Let me ponder the no pounder. Do you think your root temp. might be a bit low? I have read that too cool temps on roots can stunt growth. Nebula says:
"Many growers aim for their reservoir water to be between 60-68°F because cooler reservoir temps prevent some bad organisms from growing in the first place, and cool water can hold more dissolved oxygen in the 60-70°F range. However, cannabis can grow and thrive in much warmer reservoir temperatures as long as beneficial organisms are present to fight root rot. In fact, I personally have found that hydroponic plants tend to grow a little slower when their roots are cool, and grow fastest around 75°F (as long as you're using a supplement with beneficial organisms to kill root rot).
Of course, at that temperature you don't have to worry about root rot at all.