Tomato plant-purple spotting!

[Oliver Buckle]

Shame you lost one, but still, the one that survived will probably do better without the competition, better one good one than two poor ones.
I planted out a little patch of potatoes, four plants by three and found I had an empty space in the center with two plants growing in the next space. Tiny tomato seeds I can understand, but blooming great seed potatoes? How did I manage that