Several factors need to be considered when hens lay one or two eggs.
1. Pushing: Were they pushed to lay? Pushing hens to lay often results in one or two eggs commonly called heat eggs. They tend to be darker in color and are often laid off the perch. Occasionally the hen will lay in the nest and even set on them but alas the eggs are infertile. If a hen does this, I let her set and use her for a foster or after a couple weeks, I start re-cycling her. Normal clutches of a minimum of four eggs will likely result when she lays next time.
2. Inbreeding can result in few eggs being laid. When I see this it is when I purchase prize bird that are winning on the show bench and then the pair produces few eggs and sure enough the next year they and their daughters, even though I have outcrossed them, produce only a couple of eggs. Pay close attention to the number of eggs a hen lays and when you select your breeding birds, consider the number of eggs the mother of the hen produced per clutch.
3. Diet: By increasing the amino acids in the nestling food fed, especially methionine and lysine, the number of eggs per clutch can be increased. Typically when the hen is fed Miracle vitamin from Italy, the clutch size increases from four to five or six and a few outliers hens will lay seven or eight. But if a hen has that many eggs it is better to foster a few, as she may have trouble covering and turning them.
In the US, Miracle is available from ABBA Products. They have it listed in their computer as AA Miracle so be sure and tell them AA Miracle. (At times, I have told them just Miracle vitamin and they were unable to find it in their inventory.)