Blight on my tomatoes!

I've not really noticed any blight here - except on the tubers from a couple of vitabella potatoes. It was last week, I'd planted a few of each variety I grow away from my potato plot to save as seed potatoes for next year. Most of the vitabella tubers were affected and starting to rot and had to be thrown away. I had been thinking of growing more of those next year as they cook really well. No other potatoes have been affected including the vitabella I grew to eat.