Vegetal flavor and aromas could be caused by DMS, was there any Pills malt, if so was the boil 90 min?
Infection could be the cause too, how quick did your ferment take off? Did you use a starter? If you had a long lag time the bacteria from the stone could have got a jump over your yeast?
What type of Vegetal flavors/aroma, corn, cabbage, celery, onion, parsnip ?
Two months ago I made a cream ale as a base with chili, radishes, parsnip, cilantro, salsa verde, lime, grains of paradise, coriander, green onion, garlic, pinch of salt. It does have that vegetable taste with the heat of the pepper, not that bad of a beer, could call it a V-10
I just made a 11 gallon Classic American Pilsner, split the batch, half as is, the other half is cucumbers, radishes, pinch of salt. Cucumbers for the flavor, radishes for the zing, kosher salt to round it out. I wound up using five cucumbers, peeled, sliced, de-seeded, then into a food processor as a green Slurpee, which was poured into the primary fermenter on the seventh day.
My last concoction was based from my Doppelbock, I hot steeped 1/2 oz of clove & 1 oz of cinnamon for 15 minutes, cooled, then blended into some of my Doppelbock as a Christmas beer, that turned out great.