I've found that the most common issue, if any, when you're on an appropriate rootstock for your area is nitrogen deficiency in the spring. There are LOADS of factors, of course, but most grape varieties have the bare minimums in almost any environment. Nutritionally speaking, they are fairly forgiving plans.
That being said, vitis vinifera has macro and micro nutrients just like humans. If you do a soil test, be sure to check for these:
Macros: Nitrogen, Phosphorus, Calcium, Potassium, Magnesium, Sulfur
Micros: Iron, Manganese, Boron, Chlorine, Molybdenum, Copper, Zinc, Cobalt
These are in order of the most common lacking nutrient, Nitrogen being the most common of all AND the most consumed year over year, this is why you were recommended 46-0-0. There's a very good chance you really don't need anything but Nitrogen and could make things worse by adding too much acidic stuff like Sulfur. I always tell folks that if you're unsure, use a gentle neutrally balanced fertilizer--something you'd use on your lawn--like 11-11-11, etc., and don't place it too near the trunk base. The best way I've found is to use a cheap liquid fertilizer injector on your drip irrigation, they do a GREAT job of diluting your fertilizer for you.
My last recommendation is to never screw with your micros or ph altering nutrients unless you've had a very thorough soil sample and have a clear and obvious deficiency. Nitrogen, Phosphorus, and Potassium are almost always ok in moderation.
Good luck!