Do not use MG anything(except their peat moss/perlite). Find a hydro store near you and get a 12 quart bag of Fox Farm Ocean Forest for less than $10. It is all organic and way better than anything you will find at Home Depot or Walmart. If you do not have a hydro store near you, the mix by big girl is in right now is from all Home Depot products, and still less than $12. Get an 8qt. bag of perlite($4.50), a bag of peat moss($4.50), and a 40lb bag of cow manure/organic compost soil($1.50). Mix at a rate of 25/25/50 respectively.
My indica girl grew very noticably faster than one of the same strain and 100% soil. Now that she is in flowering she has grown over 8" in the past 8 days.