Mystery in the Vineyard

We have a mystery in the vineyard. This year is very much like last year with respect to the amount of rain that we have been having. On the one hand, we don't have to irrigate, but on the other hand, with the rain and the sun, the amount of vegetative growth in our vineyard was out of control. While we did our best to control this growth and provide for air flow in the canopy, it was not enough to prevent the spread of downy mildew which we typically see in our vineyard.
This year, however, we are seeing somewhat of a puzzle. All of the varieties that are on the east side of the vineyard have really lost their leaves. This includes the Chardonnay, Cabernet Sauvignon, Cabernet Franc and Barbera. Coincidentally, when my husband sprays, he begins at the Chardonnay and goes east to the Cabernet Sauvignon, Cabernet Franc and Barbera. So, for a while, we were thinking that there might be something in this order of spraying.
This weekend, while working with our friend Laurie, I showed her the difference in the canopy between the Chenin Blanc and the Chardonnay which is illustrated in the photo the below.

To me, this photo shows that no matter where the Chardonnay was growing, it experienced the same problem of loss of leaves as the Chardonnay planted together. To add to the mystery, this year, knowing that the Chardonnay is prone to downy mildew, we aggressively shoot thinned leaving only enough shoots to carry a nice load of grapes.
Right now, we are shrugging our shoulders wondering what we can do next year which might lead to a different outcome from the mystery we have in the vineyard this year.