Cucumbers should be started no more than 4 weeks before you plan on setting them out. Cucumbers also do not 'like' to be transplanted. Probably shock from the disturbance of the roots is causing your problem. Just keep an eye on them; they may recover. If they don't recover start some more 3-4 weeks before you plan on setting them out or direct seed them in the garden. Zucchini should be direct seeded.

Jon

Agree - as Jon said, both much prefer to be direct seeded and are very susceptible to transplant shock. If transplanted, it should be done before the second true leaf develops and then only once. Transplanting later than that often stunts the growth and reduces production.

These may recover but if you find you have room in the garden for more plants try direct seeding some once the soil temp is above 60 for better results.

Dave

When transplanting Cucs, don't bury them any deeper than the root ball. I found if you plant them deeper & cover any of the exposed stem, the stem rots at, or just below the soil interface. As the plant grows tougher & the stalk touches the ground, it may send out a new root where it touches the ground but don't cover it. The surface of the seedling plant soil should be the surface of the soil in the larger pot. I learned that one year when I lost 6 nice plants when I put them in the greenhouse & buried them like I do tomatoes.
Good thing is cuc seeds sprout pretty quick if you soak them in water before planting.

Is the new potting mix really dry? Maybe they need to be watered.

Transplanted indoors or outdoors? If outdoors, there's also the risk of them being insufficiently hardened.

Umm... karenrei and jessicavanderhoff; The original post states she "transplanted them into 16 oz plastic cups", and "I watered them all with a very weak dilution of Terracycle fertilizer"

Are they looking any better now bellamama02?

Jon

hatchjon: Why do you automatically assume that the cups were indoors?

When I do grow cucumbers or zuchini's, I never transplant. I always start the seeds in a normal large (and wide) container.

karenrei: Good point. I think I fell into the trap of assuming his climate was like mine, i.e still snow on the ground.

Jon