I know this is probably a dumb question, but you did give them a good soaking right? If not, that could be it. I grew cucs for the first time last year and they are very thirsty plants. Might be when you replanted them, the dirt surrounding would have soaked up any water from the original dirt it was in.
Now if that's not it, did you mess with the root system much when transplanting or did you leave the whole root system intact from the original pot and just set it down in the new pot? If you did break off the old dirt from the original pot and/or you broke any of the little roots off in the process, that will cause the plants to suffer a bit. If the damage wasn't too bad, it shouldn't take them long to recover and start growing