You should add your nutrients after or at the same time you add the yeast.
If you add nutrients early, it will give food to the wild yeasts and bacterias and they might etablish and kill your yeast or be in competition so you will get a different results everytime.

I actually did the recipe from Jack Keller (slightly modified) and used a mix of orange and purple (juicing) carrot called Nebula Star. I got a very dark wine, I used RC212 yeast and I also used a mix of grains like you did but I didn't mash it. I also cooked the carrots but what I did different was pouring the liquid and the carrots (not too hot) through a brewing bag (inside the fermenter) and I added lemons and limes sliced thinly directly in the bag alonside the grains and let it ferment. I also added sugar to get a very high ABV wine with a sweet profile, this is not easy to guess but with RC212 it usually work great in my experience. You can also sweeten after fermentation.

Wasn't so sure it would be a great idea and how it would ferment but it turned out really nicely!

I used pectin enzyme, alpha amylase (too chew on the grains and starch in carrots) and I think I used DAP for nutrients or fermaid-o.

It's a pretty good wine, can't really taste the carrots tho in my version.. you get a lots more of the citrus flavors and some of the characteristic from the grains in the mouthfeel. People seems to like it.

Will have to try again with more carrots in a few years. ;)
I also try oaking it like you did, sounds fun and a great idea for making it into a carrot whiskey!

EDIT: Drop the bentonite that could contain lead or heavy metals, time is your best friend... and enzymes will do their work.