The buckets start by themselves most of the time. If left alone, often they finish dry and turn out quite well, but not always. Just add a competitive or nearly any strain of commercial culture to insure it finishes well. The yeast will have no problem assisting or finishing the final high alcohol at the end.
A small nutrient addition is helpful, as it is clarified juice, usually on the low end of nutrients. I dont know why you are adding bentonite to juice, which is usually crystal clear, and is not needed. Sulfite is un necessary as it is juice which is quite stable and not high in bacterial colonies, and the yeast are very insensitive to it. The best you will do is stress them further adding it now, if enough is used to have any effect on them.