dutchman said:Fertilize with what?
There isn't going to be any consensus between everyone as to what specific product to use because everyone has their favourite and often there are different circumstances, such as seedlings in soilless mix in a container would need more nutrients supplied than seedlings in soil in the garden where most of the nutrients are available naturally and fertilizer is more of a boost.
Assuming in pots, and they've been germinated for a few weeks (they don't need, and shouldn't have, fertilizer while germinating and have enough stored in the seed to keep them going for a few weeks once they're up) then you ideally need to provide all the essential nutrients.
Those would be nitrogen, phosphorous, potassium, calcium, magnesium, sulfur, iron, manganese, zinc, copper, iron and maybe molybdenum. If you can find a fertilizer with all those listed (except calcium and magnesium which are usually provided in the medium as dolomitic limestone unless you made your own, they aren't usually in fertilizers) you're good to go.
If you're growing them in the garden then you'd look for a general all purpose fertilizer. You may nor may not need to provide the micronutrients (the last six in the list above) or the secondary macronutrients (calcium, magnesium, sulfur) depending on what's naturally in your soil, so something with just NPK may suffice. In fact even just nitrogen may be enough (it's the nutrient most often limiting growth) but the best thing for growing outdoors (or in a greenhouse if on a commercial scale) is to get a soil test.
