digging up rotten potatoes :( why?

[Two_Sheds]

actually they were from the corner shop lol, couldn't find any seed potatoes

Ah. there you go then.
Paying for seed potatoes may seem a rip off, but they are certified virus-free.
your corner shop spuds may have had something nasty lurking in them, which came out once they started growing.

[jaykay]

I think my potatoes have suffered the same as lynda66's. I put it down to the rain (constant for 2 weeks while away on holiday and still raining in the week we've been back). The plants looked healthy before I went away, no signs of blight or disease, but the tubers have been mostly mush, white mush that didn't really smell. I did use proper seed potatoes but was a bit late planting out so concluded that as they were first earlies they should have been in, and out, of the ground sooner.

[markwcel]

could be hollow heart...something to do with wet weather after a dry spell