The cotyledons (a.k.a. "seed leaves") are still attached. The purpose of cotyledons is to feed the sprout until it develops enough true leaves to get photosynthesis going and root system developed enough to absorb nutrients from the soil. You do not need to fertilize as long as the cotyledons remain attached. They will ultimately dry up, shrivel and fall off - that is the sign that you can begin fertilizing. Even at that point, use a starter fertilizer that helps develop roots and stems, and only use 1/10th the amount on the label. Very gradually build up to full strength - very gradually. After the plant gets several sets of true leaves you can switch to a foliage-producing fertilizer. Once the plant shows first signs of buds, you can switch to a fertilizer that promotes budding, flowering and fruiting. Note these are rough guidelines.Â
Â
I like to use the analogy of a human baby - you don't give human babies anything stronger than human milk to start with and you only give them small amounts. You then start introducing solids that are nearly liquid - wet cereal, pulverized peas, etc., and gradually increase the amount. Then you go to a mix of part soft solid, part liquid and eventually go to real solids. Even a 5-year-old eating real solids can't eat as much as an adult can eat. Everything has a time and amount when it is appropriate and a time and amount when it is not. Same with plants and every growing thing.