If polystyrene are those little balls used in packing, then I've heard of people using them before, but you'll want to find a way to sterile them first. Any eggs or mold spores that have gotten on them will cause problems down the road. Perlite is really a better idea, and it's cheap. I bought a 3 foot tall bag for $18 at the nursery. But don't use any that include nutes, I think miracle grow has 1 with nutes, avoid it.
That's also a lot of compost to use, depending on how hot it is of course. Not bad if it's weaker, like a 8-8-8 rating. But if it's 20-20-20 then it's way to hot to use that much. You should get them in new soil ASAP anyway, miracle grow is known to cause major headaches. Sometimes it's fine and other times it can kill your plants, you can never tell so it's better to avoid Miracle Grow all together. If they ever come out with a soil designed especially for MJ then I might try it. But the dirt they make now really isn't made for MJ.
If you want to use something that comes premixed with some good stuff so you don't have to add nutes for the first month or so, get yourself some Fox Farm Ocean Forrest. That stuff was designed for this type of plant. If you mix it with perlite (1/3 perlite, 2/3 soil) you can make three 5 gallon pots with 2 small bags that cost under $10 each. As long as you don't fertilize you're burns should go away, but if you're using all that fertilizer, then those are nute burns, no question.
For future reference, Foxfarm is a little too hot for seedlings or clippings. For getting seedlings or clippings established you'll want to start with something weaker in a cup (don't use see through cups, light damages roots). Once the roots are established (a few weeks) you can then transplant them into you're 3 or 5 gallon pot with Foxfarm. Best thing to do is to go to a nursery and ask the horticulturist what he/she would use for fern clippings or seedlings.
CFLs shouldn't burn plants. The only thing you might have to worry about is heat. Not on bulbs 32w or less, but I don't know how strong those new bulbs are. A good general rule for heat, if you put your hand under the bulb by the plant and the heat isn't uncomforable for your hand, then it's ok for the plant. You might also want to get a thermometer, the optimum temp for photosynthesis is 72 to 80 degrees. Plants will grow fastest in that range.
You have to seriously stop using so many nutes though, remember this is a weed. It can survive in some pretty harsh conditions if it needs to. All you want to do is to try to make the conditions as comfortable as possible so it can grow with as little limiting conditions as possible. If you transplant into Foxfarm, don't fertilize till your girls tell you they're hungry. They'll even tell you what they're hungry for. When you see some discoloration on the leaves just look up which deficiency your looking at, then add some nutes that include that nutrient. Here are a few good links to use to figure out which deficiency it is. It also has pics of other problems, it's good to try to familiarize yourself with what different problems look like.
https://www.rollitup.org/marijuana-plant-problems/157345-have-plant-problem-check-here.html
https://www.rollitup.org/marijuana-plant-problems/216537-self-diagnose-your-plants.html
http://www.ganjaguerrilla.net/Album3.htm
Plants can get pretty huge, depending on the strain, growing conditions, room for roots & ceiling space. Because of room for roots & ceiling space outdoor grows have produced the biggest plants (see pic 1). Plants like this aren't a good idea though, it takes too many seasons to grow it that big. Every season the plant goes into flower and then back into veg, this is called regenerating, and you loose potency every time you regenerate. That plant is probably a "Meixan Schwag" tree.
The next two are indoor grows, the first one is still in veg and the second is ready to be harvested. This is about the best you're going to do indoors in 4 months (2 mo. veg & 2 mo. flower). A technique called FIM was used on it, you'll only get 1 main cola if you grow without any growing techniques.
