The leaves that you refer to as non marijuana leaves, are termed embryonic leaves. Them yellowing and then falling off are normal.

I couldn't help but notice that some of the leaves of your plant are displaying characteristics of fert-burn/over-fertilization (burned looking tip, downward leaf curve, dry and crispy to touch).

You're using Miracle Grow aren't you? Those soils come too concentrated for cannabis. I probably would have recommended baking dirt from outside to use.

Soil leeching could help.

Yes, you do need better lighting. And if you were to buy more cfl, please purchase those of a warmer spectrum. These will help with the most important phase of the plant. The flowering stage.

Your plants look sativa dominant to me. I'm guessing that they may double in height when you initialize a 12/12 cycle.

I've never grew before, but have researched a lot.