Hope you don't take this the wrong way but.. for starting seeds.. get the seed starting soil mix. When plants are young they don't need any extra nutes. Once they get a few nice leaf sets, they could be transplanted into the miracle grow potting soil that feeds plants up to 6 months, or you can continue to use the seed starting mix if you'd like so you can control a more precise amount of nutes.

Basically the most important thing is not to feed seedlings nutrients, including soil nute additives. Your plants will yellow and fail. Feel free to ask anymore questions you come across, people are more than welcome to help here, and its better to ask a question and succeed than venture blindly into cannabis growing and waste a lot of time and work, only to have poor or dead plants. Good luck fella