Hi Ruan,
You have to be careful not to over breed birds. You only have the previous owner’s information she gave you, but this could be a pair that has been bred so much they won’t anymore. I would take down the nest box and rest them for several months. Then you can replace the box and try again. You need to be feeding them a nutritionally balanced diet like seeds or our foraging diets – a loose seed mix will not provide the nutrition they need. You should also offer chopped veggies, leafy greens and some fruit. When you get them ready to breed again, start offering multi grain bread and cooked eggs, with the shell washed, crushed and cooked with the eggs. Only offer these foods when they are set up for breeding and until any chicks are weaned. You should always remove the nest box as soon as the chicks leave it, and do not put it back for about 6 months. In captivity, you should only allow up to two clutches per year, which is one more than they would have in the wild. Never leave the nest box up all year. Adult birds do not sleep in nests and only use a nest for breeding and hatching chicks.
Thank you for asking Lafeber,
Brenda