You have to be real careful when it comes to soil/soilless mixes, you have to make sure that that soil doesn't have any nutrients in it that can be released at any time. You also want to make that you can get a soil/soilless mix that has a neutral ph balance to it. The curling up of the edges of the leaves could be a few reasons, one could be from over watering and two is the moisture isn't being displaced fast enough or maybe even a heat issue. I have used "Roots Organic Coco Mix" and didn't like it and now I'm running "Pro-Mix HP" and so far everything is going smooth but...I favor hydroponics.