When they look healthy like that they probably don't need any nutrients. Not only are they healthy, but they appear to be about two weeks old. Plants usually don't need feeding until they've been in their soil for three weeks or more.
Some people wait until their plants manifest signs of deficiencies before feeding them. Others go by a schedule and fertilize accordingly, unless they encounter problems such as over-fertilization.
Wait until your plant is about three weeks old or so before feeding it. It is advised to feed at half strength and gradually give it more over time.
Do a lot of reading about fertilization as well as all the other basics of growing. There is a lot of information on this site, Actually, I like this site better than my grow books.
Your plants looks really nice.