Get used to not catching much in the daytime,because it will mostly be like that. You dont want to get the dogs too used to loosing or they will loose belief in themselves.. Young dogs need success.
Take one out at night with a lamp and give them the easiest ones you can find..If they have myxy all the better..At night they will get farther out and have further to get home. When you catch for the first time,stop and take the dog home. Once they have had success missing a few in the daytime wont matter,but try not get them used to just chasing time after time without getting a catch.