Sounds like you've gotten some good advice so far. Just follow the basics if this is your first time. A couple of the basics that have been pointed out already:
1) Your plants are young and focusing on developing roots, they will soon push out a bunch of leaves. While they are young, you won't have to worry about adding any nutrients. Make sure you are familiar with your growing medium and nutrient combination...so much to read, so many options, so many variables...good luck on that end, but for now, just give water that has been set out for a few days to evaporate some chlorine (unless you have well water). Set your water to 6.5-6.8, 6.8 works for me, but be consistent whatever you do.
2) Don't over water. When you have watered enough, some water will come out the bottom of the pot (switch to smart pots). You will judge when the plant is dry in two ways. First, the entire unit will be significantly lighter than it was when you put the water in, how much lighter? A lot lighter. Second, when you jam your finger down in the dirt, it will be dry. Not moist, not damp, not a little moist, but dry. Know how to tell if you are in danger of being too dry? Your plant will be drooping and you think you've certainly killed her...even then water will bring her back...trust me. DON'T OVER WATER. Seriously, not trying to be a dick, it's just a common mistake, I don't even know if you have, just don't. After you've jammed your finger in enough pots and compared it to the weight, you won't have to jam your finger in any more pots. Do your roots a favor though and switch to smart pots or some other cloth pot, it's just the way we do things...super secret tip...they're machine washable if you get the majority of the dirt out or don't care about your washing machine. ***obviously without detergent***
3) Don't re-invent the wheel when it comes to your nutrients. You can find 1.566 million variations that have been tried and are sworn by: eek, they will all work to some extent! If you want simple and proven then it's smart pots, promix HP without fungicide, Fox farm grow big, tiger bloom, three part soluble. Fossil fuel. Dark Energy. Superthrive. During veg: superthrive and grow big every other feeding at 6.8ph (straight water in-between). Cut Superthrive two weeks prior to flower. Follow schedule from fox farm disregarding their call for additional nutrients or flushes, begin flower nutes one week prior to flower, enter flower on straight water under new lights. Flush with double waterings 1.5-2wks prior to harvest...that's a simple method that works. Be rigorous on your PHing, don't get sucked into the "it's a weed, it grows all over"...yep, it does and ditch weed is stringy and has beaners, nobody wants that.
Have fun man, whatever you do, it will grow. You can, however, have a lot of control over how well it grows!
you're getting this problem because of you...you are doing way to much to that plant...first you never start feeding until the cotyledons are wilting and the lower leaves "start" turning colors then feed her 1/4 strength nutes (what the manufacturer recommends)...and don't over water this could cause root rot...and next time fill that pot up don't be shy with that soil...the deeper the soil, the deeper the roots...good luck and welcome to RIU 
...Miracle Grow is not one of the #1 brands cuz it sucks...it's cuz it works...I would amend it a little with some garden lime and epsom salts, but I use a super soil myself, but it's a little more pricey...peace...
