First feeding

Check what nutrients are already present in your soil !!! <--- The seedlings have nutrients stored in themselves for 10 - 14 days of initial growth after they sprout. After that they will use what is already present in the soil. If you are using a high quality soil with plenty of nutrients in it then you probably won't have to feed her additional nutrients until she is 4+ weeks especially if you are repotting into bigger pots with fresh soil more than once in that time. Monitor the bottom fan leaves for yellowing as the best indicator that they are seeking food as unless the bottom leaves are completely shaded from light the plant is taking the nitrogen from the bottom leaves to fuel it's upwards growth. I recently experienced overfeeding my first plants and it was really not fun watching them start to die and the process of fixing the problem cost a lot of extra effort, time, and money. More food is not always better. Good luck and have fun! :)