a pH tester will be invaluable for your endeavors in the future. Fish emulsions, bat guano, bone meal are all excellent sources of additional nitrogen. Your local hydroponic store should have them. Make sure you get the type that is for soil not hydro.

You need to wait until your soil is relatively dry before watering again. Since you haven't been feeding them yet you don't really need to be flushing right now. I would just get some nitrogen additives and check the pH and you should be in good shape.