Jeff,

I had a similar problem where the leaves took on a purplish outline as
well. Like Joe, I also figured on potassium deficiency, and saved my
fireplace ashes that winter. A large cupful scattered under each vine
every few years keeps the problem at bay. It works for the small vineyard.

[Thought I posted this several days ago. Sorry.]
--


Mike MTM, Cokesbury, New Jersey, USA