Small potatoes

.

Have just finished digging my main crop potatoes, Sante and a row of Rooster for roasting!

I found with both varieties I had a lot of small, small hen sized tubers, although normally I get some but this time there is lots!

Any ideas would be appreciated, as they were fertilized as normal and we had lots of rain during the growing season!

What else could go wrong as they were rotated from last years patch?

Cheers!