DO NOT USE A PH OF 6.6!! that is a ph for soil. And while that will work amazing in soil, it will NOT work well in your Sunshine Mix #4. Please do not give advice unless you are 100% certain and have tested products that are being talked about.
YOU NEED A PPM METER!! Don't be cheap! You might be hungry, but your plants are starving! (but seriously, buy food for yourself before your garden)
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Ca/Mg is 100% necessary and you should be using it. You can use the organic ca/mg+ from General Organics, it would go well with your line up. If you can't get to the hydro store today, you can use molasses, it is also a carbon and carbohydrate supplement, as well as providing Ca, Mg, S(sulfur), and K (potassium) which are very improtant. Ca/mg is most important during the flowering stage, so while you may not SEE any problems now, you will later, and your plants could be a lot bigger and tougher right now with ca/mg. molasses will make your ph act funny, and your reservoir will sour quicker, but your plants love it. It's the "secret ingredient" in most organic liquid fertilizers.
Keep your ph between 5.8 and 6.3 More nitrogen is available at 5.9 and more potassium/phosphorus is available at 6.0-6.3, ca/mg and I believe sulfur are all available at a higher pH of 5.9-6.1 but I'm reading through a few books right now to be sure.
You want my best advice? Throw the Fox Farm in the trash and buy a TechnaFlora kit for 35 bucks. Fox Farm is more for growing fruits and vegetables.