If it's Fox farm Happy Frog ... my plants went to the start of flower without any supplemental feeding at all. The soil already has mycos. The fish fert is not very useful imo ... you want something more balanced with some P in it. Are you gonna grow strict organic, or are salt 9solution) nutes OK? With a quart each of General Hydroponics Flora Series and a pinch of Epsom salt, i fed my ladies through the end of flower.
Under a 400, with your space filled (3x3?) by the time you flip your lights, as much as 8 ounces, but on a first grow expect 3 to 5. I would not run your veg on a strict schedule (although i know it's tempting) but do the flip when their size is right, just filling the lateral space. cn