Taters in containers!

perhaps they just needed a little longer to grow? None of mine are ready yet

Well watered is your problem. They need to be drier which encourages more tubers. Lots of watering encourages lush top growth at the expense of tubers - you get only one or the other, never both. And also go easy on fertilizers which also encourage top growth. It's the soil you want to feed with some rotted manure and/or compost, not the plant. Try it again with the changes and it'll probably yield better.