Did you trim around the seed potatoe and let them dry out..before planting them.......amending the soil that you use for potatoes is important.....watering until the container runs out the bottom to keep them moist but not soaked. When I cut the potatoe out before planting I cut around every tiny bump that is where the seed starts into the potatoe root.....when my spouse does that he only cuts them in half and in half again.............he gets only 4 potatoes per potatoe.............I can get 10 to 20 sometimes more.....