It can take 2 weeks to develope roots depending upon temperature is my diagnosis, keep them warm, get a clone heat pad put a towel between the heat pad and the actual rockwool may get to hot, patience is key in growing, do not over water and dilute any thing you add to it, you can "lock" up your medium ( rockwool " or you already may have with adding stuff to it too much in an effort to stimulate growth.. just let her sit, keep her warm humid and moist,, just like any other girl

Rev Kevin