Thank you. Over-fertilizing may indeed have been my problem - such as using too much of my garden soil, which probably has too much of a compost component. I’ll have to give your suggestion a try this year.
It should work. Potatoes thrive in nutrient-lacking soil. Ask any Potato Farmer who plants in the same field year after year after year. (i.e. The entire MIDDLE section of our state. Wisconsin grows potatoes only second to Idaho. Thank the Glaciers for that sandy loam.)
They also like well-drained soil, so lighten up the in-ground soil with bagged peat but don’t add sand - you’ll get cement!
Make sure you have good drainage in your potato buckets. If using 5-gallong sizes, drill drainage holes about 2” up from the bottom of the pot, all the way around, or if your pot has bottom drainage, make sure it’s sitting on bricks so it will drain properly from the bottom.
OK. I’m done! Now you know everything I know about growing potatoes. :)