Right about blight?

Calling all potato heads, does anyone know what blight looks like? A couple of our Roseval plants wilted and showed spots like the leaves below. We dug them up and disposed of the stems (though I couldn't resist eating the very pretty potatoes). Obviously, if everyone agrees it is blight we will bite the bullet and rip it out, but do we need to take them all up, if not what is the best practice. The rest of the plants are looking pretty healthy, aren't they (see the bottom picture please) or am I just being an ostrich?