I have just noticed the new shoots on Leon Millot, Baco Noir and L'Acadie...
I have just noticed the new shoots on Leon Millot, Baco Noir and L'Acadie Blanc are turning black at the edges. This seems to be confined to the new shoot at the tips of the canes. It is not on all - about 50% are affected. I see no signs of powdery or downy mildew
I'm going to answer your questions with more questions. Could you please submit a picture? Are the apical meristems (tips of the shoots) still intact, but black? Are the shoot tips black and wilted? What kind of winter did you have? If you had a severe freeze event, the shoots could be collapsing, or crown gall (look for tumors near the soil line) could be causing the collapse of the vines.
It could be Botrytis shoot blight, if it looks something like this: http://www.ipm.ucdavis.edu/PMG/B/D-GR-BCIN-BT.003.html
If you submit images, that might help point us in the right direction.