Worried about spuds

Hi all! Hope everyone is well, haven't been on for a while so new site design took me by surprise, Anyhoo! We planted Charlotte's, Jersey Royals and Maris peer in late March, earthed up a bit when it got nippy, no probs there! just noticed this morning discoloured floppy foliage on some plants, mostly on the Charlotte's and Peers but nothing on the Jersey's, If it was frost wouldn't they all be affected. Bit concerned as I haven't actually seen any sign of frost at all. Thanks Ian

Just as a matter of a pedantic point.

Jersey Royals can only be grown in Jersey. I assume you've got International Kidney. 

Jamboian - I have two types of spuds growing in pots on my path both were effected by the frost but one type hardly at all while the other was really messed up. There are still bits of fresh looking green on these so I am hoping they recover but I wish I had recorded which is which because it does seem as if the other type is a bit more frost resistant.

I was away last weekend when we had a heavy frost. I've noticed my spuds are just pushing through the surface and are browny black! will they recover? regards Kev