PaulF said:What is your growing medium? It almost looks like peat moss or sphagnum. They should be in soilless mix that is fairly neutral pH. It seems like they need some nutrients. A little plant food (the blue powder mixed into water) at about half the recommended strength will green up the leaves. You are correct not to water too much, only when the soil is a little dry.
Newyorkrita said:Cucumber seedlings really hate to be transplanted. Really don't want those roots disturbed. See the new growth coming in the center of the plants? As long as that is healthy the plants will be fine. They don't need the baby first set of leaves anyway.
Newyorkrita said:Like a seed starting or potting mix.