You don't need to add any
nutrients to germinating
seeds. Once they get big enough, I would use a diluted
nutrient solution (about 1/4 to 1/3 max). What type of seeds are you germinating? What type of system are you planing on putting them into when they get big enough? The pH requirements vary from plant to plant, but generally 5.5 to 6.5 is fine for most plants. In which case I would aim for 6.0 so it can fluctuate.