What do the instructions for your nutes tell you? You probably won't need to make up as much as 4 litres, 2 litres would prolly be good. But you really don't need to add nutes to a seedling as it's getting all it's nutrition from the cotyledon leafs (first round pair of leaves made from the seed). Then you only want to feed it very little at a time until it's established. Just make sure you don't overwater. It's the easiest thing to do, as it's all you can currently do to look after you plant. If you feel the urge to water your plant spend time breathing on it instead to give it co2.