Fertilizing Seedlings

Now that my seedlings have spouted, should I be adding some fertilizer (or plant food) into the water? If yes, what do you recommend?

For most culinary herbs a dilute solution of an organic fertilizer, such as deodorized fish fertilizer would be a good idea to speed up growth. Manure tea is also a good option as a source of nitrogen. In any fertilization programme remember that any nutrient missing from the supply the plant has access to sets the limit to any possible growth. The plant cannot use the other nutrients available to it once one nutrient is all used up or not available in an usable form.
It is better to fertilize more frequently but with a much diluted fertilizer, than fertilizing infrequently with regular strength fertilizer. The plants will use more of the food (less will end up in the sewer) and the chance of burning the roots is much reduced. Also as the plants reach maturity it is a good idea to stop or cut down drastically with the fertilization, because hungry plants have more flavour and in the case of medicinal herbs, produce more of the medically active ingredients as a reaction to a bit of stress.