I have done something very similar. I'm no expert but here's my experience. 1) Go super light on the Miracle-Gro and nutes. Since it's already in the soil you wont need to do much else. Just my two cents, others may disagree. I think it's far easier to cause problems with Miracle-Gro and strong nutrients than it is to solve problems with them. In retrospect, I think I would have been better off without any EXTRA nutes. 2) I've been surprised how differently various strains react in a contained environment. I have Sativas thriving in the exact same conditions where I have an Indica of the same size and age suffering. My experience is you just have to go slow and monitor the ladies. 3) Neglect them rather than pamper them. Again, this was just my experience. When I tended to them regularly they did worse than when I just did what I thought was the bare minimum. 4) My growing really improved when I started chatting up the guys at the local hydro store. They got me on better nutes and mediums. The stores here also give away free worm tea. For me, tea seems to do the ladies better than strong nutes. 5) Lastly, I think it's wise to follow the instructions on the box of nutes. I don't though. I just feel like it's too concentrated. Over time I've found it best to use a little less than instructed. But more is better, right? That was not my experience. Especially when they are young, I go very, very easy with soil nutes.

Good luck! Hope I was of some help. Disclaimer: I've only grown about a dozen plants and they haven't all been perfect. So take my comments with a grain of salt.