Pitiful Potato Harvest

I pulled up my red potatoes today. And got a whopping 10 1/8 oz worth of potatoes out of 4 plants.

Red potato harvest

Grr. I had a really small Yukon Gold harvest, too. I'm not sure what the problem was. I don't think the plants were too crowded or close together. I''m wondering if maybe the ground was too hard for them to properly spread roots and grow, but it was soft and freshly tilled when I planted and all the dirt I used for hilling was also soft. During the growing process, only one plant flowered, and only a couple blossoms at that. Something was definitely amiss. Will have to do some research and see what I can change next year for a better yield.