If your willing to pay for it, you can buy remineralized topsoil at bamaplants.com. I bought some and used it in several new tanks. The color of my plants exploded about one week after I set up the tank. Unfortunately that tank experienced a catastrophic structural failure and had to be replaced (see pic). Someone actually gave me a replacement 55g tank 2 days later and I was able to remove the substrate without disturbing the layers of rmts, sand, and flourite. But I digress...
There is also the option of diy root tabs to complement your rmts. I use capsules filled with osmocote plus and/or root growth hormone. Bamaplants will take care of you, just let them know what you need.