Since no-one answered you yet, I will give you the benifit of what little I know or believe. (If nothing else it should move you up in the ratings again)
Around here no-one does anything about manuring, I always thought they grew on poor soil. You will probably have lots of growth next year.
I have 3 vines growing close to, even under, the house. All did well this year, but last year there was a cold snap that did away with almost everyone's crop. Certainly the grapeyards didn't produce.
I would put my money on the early weather before anything else.

Phreddy