I looked at that, but all the info I found said that Hollow heart developed in storage rather than as in these, being there when first harvested. It also said that the tubers would not store, but begin to rot, the pictures were taken today so they are not even remotely beginning to decompose. Very odd. There is another condition which I found which is similar, though the discolouration seems greater. the cause of it is posted as unknown, presumed mineral deficiencies. It is listed as Internal browning.
Thanks again.