Congrats with the hatch! What kind of nymphs are they? The nymphs might not eat for the first two days or so, so don't worry about that. Generally speaking, you may give them a light spray of water, but make sure the droplets are very very fine, because little nymphs have been known to get trapped - and even drown - in drops of water!
Most nymphs, with the exception of some really tiny species, should be able to handle D. melanogaster fruit flies. I'm not familiar with springtails, but perhaps some of the online places sell them.