Hi skater...
Welcome to MP!
You definitely got the goods! If you came on here and asked if someone could suggest a great setup that will yield top quality buds they would recommend all the stuff you bought... good job!
Even after 15 years of growing I sure wouldn't consider myself a pro but I've learned many ways to grow dank bud and probably more ways to screw it up!
Do you have good ventilation and air exchange in your grow room...? Fresh air is very important to plant health and temps should preferably be kept in the low to mid 70's and not warmer than 80º for flowering if you can avoid it. Strong fans in the grow room are a must. They strengthen plants, help them transpire and will help keep problems from starting at the soil level. Make sure you water thoroughly and then let the top inch or so of your soil to completely dry out between waterings. This will keep help prevent pests, fungus and pathogens from getting a foothold in your garden.
Your 600w MH is ideal for vegging. I suggest you buy a HPS conversion bulb for flowering though. Keeping you plants close to the light will encourage more compact, tighter growth but it's going to be hard with that many plants in your grow... 20? That's quite a bit for 600w unless you're going to just use this space for veg growth. It's going to be way too crowded in there for a 600w light. I would flower 4-6 plants at the most when they are about 15-20" tall. Plants grow 2x - 3x or more in height when flowering.
FFOF is a very high quality organic soil and your plants will be fine without any nutes in that soil for 4-6 weeks. If you feed them any Grow Big mix it at 1/4 or 1/3 strength to start with because the FFOF is such a rich organic soil and has everything they need for vigorous growth. When you flower also start with very weak 1/4 strength mix of the Big Bloom and Tiger Bloom nutes and slowly ramp up the strength until week 4 of flowering and then slowly ramp down the nute strength until a week before harvest and then only water until you give them the chop chop. In a soil that rich you'll do better to feed them nutes only every other or every 3rd watering or you'll risk overfeeding them. I've seen very dank bud grown in FFOF without any added nutes so use them sparingly.
Have you thought about odor control? Strong ventilation and a carbon filter are the way to go... It's the best investment you can make in your grow next to a quality light. One plant can really stink up an entire house when you're late in flowering if you don't have ventilation. Stagnate air is your enemy because odors will build and build until they come out of your grow room, down the hall and throughout your home. It WILL be an unwelcome conversation topic if it's not kept under control...
Like Irish sez... don't tell ANYONE. But even if your grow is very stealth, without odor control everyone will know about your hobby the second they step into your doorway if not before...
Peace!
