there's no point in feeding a plant individual nutrients like only nitrogen. these plants need over 14 different nutrients to grow so what you need is general plant food. hydroponic grade nutrients would be best but if you have nothing else, go to home depot and buy what they have. It sounds like the food you have will work as well. You're looking for a grow formula with 3 numbers on it. My brand is botanicare cns formula and the ratio is 3-2-4. the numbers equate to 3N (nitrogen), 2P (Phosphorus), 4K (Potassium). Any ratio value in NPK similar to that will help.
I'm sure you know by now that plant is looking like a 2 week old instead of a two month old. The main things all plants need to grow indoors is light, nutrient solution, and air (co2). If you have adequate air circulation, and your computer fan sounds fine, co2 is covered. Feed your plants with your nutrient formula every third or fourth watering and you have nutrients covered. In my opinion, if you're using cfl's or any kind of fluorescent lights they should be about 4 inches away from your plants. I would watch your plants closely to make sure that's not too close as your plants are still fragile.
Hope this helps!