Hi Cindy,
Well, D. peltata look very alike D.rotundifolia in shape and size at first: it grows a basal rosette, and then after a few leaves, get an erect stem. If i have few spared time, I'll try to post you a picture...
For the D.pulchella seedlings, I never grew it from seeds, only from gemmae, but I can tell you that they has a large petiole comparatively to lamina (sorry no pictures). Only by their size, you should be able to tell the difference between these two, D.pulchella a lot smaller than D.peltata.