Somerset, United Kingdom

All my brassica seedlings are dead/dying - Help!! I first sowed, as I have done successfully for years, in trays. Almost all germinated. I kept them indoors at first before beginning to harden off. They seemed to be coming along nicely but then, when they'd developed two of three true leaves, they began to go brown at the edges, then the seedling just curled up and died. I salvaged the few survivors and planted into a nursery bed, but they too soon succumbed. I've tried direct sowing into a nursery bed in a different part of the veg patch, but very few germinated, and those which did soon gave up the ghost. When I dig up the corpses, the roots look fine. They have a few flea beetle, but not enough to do too much damage. The dead seedlings feel crispy. I've now tried sowing in brand new trays, using only tap water, but I'm really worried I may lose all this years crops. Cabbage, sprouts, brocolli and kale are all affected. Meanwhile, leeks, tomatoes, carrots, potatoes and a range of flowers are all fine (so presumably not water/soil disease or pests?). In 40 years of veg growing I've never had this problem. Can anyone shed any light?

• 17 Apr, 2014