Potato problems?

If the tubers were large, I would think it very likely to be caused by a dry spell after wet weather and related to hollow heart. The only other thing in my 'Vegetable Expert' book is soft rot where affected tubers soon become slimy and putrid but is an infection it says of damaged tubers.

With hollow heart, I generally am able to removed the offending centre and still end up with a reasonable amount of usable potato. Obviously the way to avoid it would be to water them in any dry spell, particularly when the plants are growing vigorously.