don't use it. its miracle gro.. they don't real make their frets to be used with stuff thats gonna be consumed go to your local hydro shop and get some real soil and additives... if u dont have a local hydrostore order off the internets 1000s you will already be 15 steps further than using MG.. I'm not trying to bash you or your stuff but miracle bro is not for Cannabis.. Fox Farms is..
For the record, there is nothing wrong with Miracle Gro. I've used it on my tomatoes, basil, rosemary, and especially my bud when I don't have immediate access to my FoxFarm or my Jack's Classic. I've enjoyed above average cannabis crops with miracle gro products in many of my grows.
I am by no means saying it is up to par with FF or JC, but it is by no means obsolete.