When should I start feeding the plant nutrients?

If this is your first grow, let me share a few tips: first and foremost, forget about nutrients for now. and put them last on the list of stuff to watch for. First, learn to water appropriately, give a glass or cup of water at this stage (16 or 17 oz / 200 cc), that should last 4 to 5 days, when the soil is dry, repeat; when the soil is drying every 2 days, you up the amount of water to twice the amount you were using, rinse and repeat. Learn to transplant, in 3 or 4 weeks, you'll have to up pot, 4 or 5 times your current pot size is a good next step. How do you know your plant is ready to transplant? Even if you saturate the whole pot, the water will last 2 or 3 days and the soil will be dry again ans growth will be really slow or even stop at all. Temperatures are key to fast growth, keep them in range and the plant will thrive. Train the plant: TOP/FIM and LST, an even canopy is key to get a great yield. As for feeding, "if it's not broken, don't fix it". Let the plant feed itself from the soil, once it has began to exhaust the media's nutrient, you can start feeding, you'll notice when the plant displays the first signs of deficiencies. Do yourself a favor and get an EC/PPM pen, it will make feeding a lot easier, no guessing games about strength.