typically in slow release soils the nutrients are water soluble, and would thus drain out with water as it drained out... since its an off brand miracle grow like medium, I would imagine that they leak out fairly quickly (especially with bark in it). Even high quality, water holding, slow release, nutrient rich soils like FF recommend you start using nutes after 18-22 days (three weeks). Those leaves are a bit pale, and so long as the first few feedings are rich in b1, and well diluted (half strength feedings), there will be no burn. Start small go big, and less is more, but that baby needs some TLC. Mine are just over 30 days old, and are almost 4 feet tall...