Smokey,
Kinda hard to tell on that pic if she's(let's have a little faith here) got hairs, but it's about the right time, I had three growing and two showed around 18days and the other one took 21. How are your res temps? are the roots getting slimey at all? maybe the roots are needing a bit more bubble? I have also heard that sometimes the root stim can cause a bit of root staining.