Columbian gold, first time! Help!

Hey guys,
First Time. Got 3 plants in an approximately 60/40 FoxFarm Ocean Forest (http://www.htgsupply.com/viewproduct.asp?productID=46655) / FoxFarm Light Warrior (http://www.htgsupply.com/viewproduct.asp?productID=46642). All in a 6" Square coconut fiber pot. They each have their own 65watt CFL 6500k Full-Spectrum bulb, and there are 2 27watt 2700k Air-Purifying CFL's. The immediate walls are covered with mylar. The lights are about 3 inches or so from the tops of the plants. Up until now (day 1, they have been under 24hr light. The timer was broken, but it seems to be doing them well. Should I change the cycle or leave it? The whole grow is being done with Poland Spring Spring Water. Everything seems to be going well. A fan should be in the room soon for stem strength. Columbian gold is the strain btw.

Few questions though:
-When should they be fed nutrients and what are some good ones? I know the soil has some good nutes in there for now.
-Should a homemade Co2 enricher (the yeast thing) be added ?
- Molasses?
-Why are they so short and bushy?
-Why does one plant have a yellowing bottom leaf with small brown spots?
-Why is the soil/perlite/vermiculite turning green?
-When should I transplant into a bigger pot and what size?

ANY feedback would be appreciated. Thanks

btw, 18 days from seed.

-When should they be fed nutrients and what are some good ones? I know the soil has some good nutes in there for now.
------Start feeding nutrients after 2 weeks or germination (or when it develops 3-4 sets of fan leaves). Start with small amounts and increase gradually over time. Dont over-fertilize. Reddish-brown or wood colored random blotches on leaves is a good sign of over-fertilization. In case of over-fertilization, stop giving fertilizers for about 2 weeks and at the same time feed plain water more often than you would normally do.

-Should a homemade Co2 enricher (the yeast thing) be added ?
----Depends if you want an extra hassle or not...given the questionable performance of home-made CO2 makers, number of plants and size of plants I would not go through that hassle. CO2 enrichers are for people who would do it at more pro level.

- Molasses?
-----Never used it and probably wont use it in future.

-Why are they so short and bushy?
------Depends on genetics. If you plant is pure Indica or Indica dominant plant its going to get short and bushy where as if If you plant is pure Sativa or Sativa dominant plant its going to get tall and lot less bushy than Indica variety. Height of your grow lights also have a role in determining height. If two plants of same strain is grown under lights with one under very close to light and another under farther away from light, the plant grown under light that is farther away from plant will grow tall and thin as the plant tries to get as close to the light as possible to get max amount of light.

-Why does one plant have a yellowing bottom leaf with small brown spots?
-----The most common reasons are - over-fertilization, PH factor of soil, or combination of both, over-watering(far less common)

-Why is the soil/perlite/vermiculite turning green?
-----No clue, I used potting soil from Wal Mart and never cared about adding any additional perlite/vermiculite to the potting soil.

-When should I transplant into a bigger pot and what size?
------Plant has much greater chances of recovery when they are younger than when they are older and it is far less complicated when they are younger because you dont have to deal with all the mess of roots it develops as it grows older.