If you're not sweetening the wine, you don't need to add sorbate. I never use it, as it imparts a slight taste to the wine that I find objectionable. I rarely use the finings, either, as I haven't needed them. I also want vegetarian friendly wine, and often finings contain shellfish or other animal products.
I do use the sulfite/campden though! That's an antioxidant and preservative, and even in a very low level like in the kit, it's protective of the wine.
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