Don't use Miracle Grow soil with the 3mo supply of food. I got some strange results with it. I took what I thought was a shortcut to some weed and I won't use it again. I started some White Widow and some BubbleGum in it, the widow takes it alright but is a little hot for the BG.
I am not going to grow in soil anymore, but if I were I would go back to using a sterile soilless mix and add all my own nutes.
There are many nutrient programs out there with two or three parts. Just remember to always use much less than the label suggests till you see the results. A good place to start might be 30%-40% to start.
Keep reading and learning and you will be TOKIN
soon.