The thing I love about gardening is that there is always more to learn. I have learned that my potatoes are probably just dying off naturally. They are an early variety and went in the ground around Easter, so this makes sense right? I have also learned that potatoes don't always flower. That explains a lot!
Interestingly enough if they do flower, the color of the petals indicates the color of the skin. White flowers mean white skin potatoes and colored flowers mean pinkish skins. It is common for Verticillium to be easily confused with the culms (stalks) dying back naturally. Potatoes will stop forming once soil temps reach 80 degrees and grow best in 60-70 degree F soils.
Lastly, Yukon Golds are known for their poor yields so finding lots of tiny taters mixed in with the big boys isn't that unusual.