When you breed birds, you also have to control how many clutches they have per year because they do not receive the environmental signals to stop like they do in the wild. You need to take the nest box down in between every clutch and not allow them to breed for 6 months. You should only let them have two clutches per year – in the wild they would only have one. If birds have been over bred, they will do things like what yours is doing. This can also happen if she was allowed to breed when she was less than 2 years old. If your birds are not on a nutritionally balanced diet like pellets, you should not be breeding them. A loose seed diet does not provide the nutrition they need. They also should be getting chopped veggies, leafy greens, multi grain bread and cooked eggs, with the shell washed, crushed and cooked with the eggs. If they are not on a good diet, they will fail to feed the chicks, the eggs might be soft, the hen might get egg bound or eat the eggs which she is already doing. I would do the 6 month rest, and work on improving their diet if needed and if you plan to let them breed again.
Thank you for asking Lafeber,