You do know that light is what plants eat right? Water and Light are food. We aren't talking about food, we're talking about supplements which are ostensibly needed.damn I thinks its sooooo funny that people say young plants don't need food. YOUNG PLANTS DO NEED FOOD, JUST NOT AS MUCH... Would you not feed a new born baby, it just wouldn't eat as much right? Feed your plants and they will love you for it, just start out lite and see how much they can take.
My seedling soil is quite light too, i cant feed straight away but first week or so they definatly need it if i want em to explode growth wise plus very good for the soil organisms. Most sites recomend a seaweed or fish based boost for the soil anyway with young seedlings, quick available nutrients and soil enhancers, as long as its low i dont see that it can do any damage plus knowing your soil is important. A mistake would be starting a seedling of in normal potting soil or normal miracle grow imo seedling soils and pro mixes offer greater control from the start. PeaceWell if soil has food in it already then yes your right you don't need to feed but I use promix which has no food whatsoever so I start feeding the day they pop