I've just checked my new garden bed, and found about 5 plants looking like this. I've pulled them all out.
I planted a few brassica seedlings in autumn in the tunnel house and lost them all, they started off like this, then wilted and died!
Has anybody got any ideas what is causing it or if it's a disease of some discription?
They all got a good soak with seaweed tonic at planting and the soil is damp. If it was just this bed I would assume the soil/compost was too rich, but I hadn't added any to the soil in the tunnel house at that stage.
They were such healthy seedlings too, I hope I don't lose anymore :(