It's underneath a pathetic row of peas. There is a white kind of scummy/dusty thing there. I water with water from the communal tap, but it is nowhere else on the plot, nit even another row of healthier looking peas.
Got a pic now...
Mold or salts from fertiliser?
I have that in places on my allotment, i thought it was from the mushroom compost that was put on previous to taking over the plot