Does the cleaner have an odor to it? ... my wine starting smelling like rotten eggs a few days into fermentation.
Yeast nutrient, while not absolutely necessary, is generally good to put in. Think of it as a fertilizer for the yeast which is supplying necessary nitrogen and phosphorus. (remember, yeast is a plant) While the grapes do have some nitrogen in them, if the fermentation runs out of nitrogen, hydrogen sulfide (rotten egg smell) may form ruining the wine.
Yeast is the key to fermentation. They are in the plant family and are all around us. Many are quite useful, others can cause infections. The most common yeasts are bread yeast (used to make bread and rolls), brewers yeast (used to ferment barley, hops, etc into beer and ale), and finally wine yeast. They all work in a similiar manner, that is, they convert sugar into ethanol and carbon dioxide. In baking, the carbon dioxide is used to make the bread rise and the alcohol is driven off by the heat. (it is the alcohol that carries that wonderful smell of baking bread, but the EPA considers that a pollutant and makes commercial bakeries filter it out of their exhausts.) In brewing and winemaking, however, it is the carbon dioxide that is vented into the atmosphere (except in champagne where it forms the bubbles), and the alcohol is retained in solution. Grapes come with native or wild yeasts living on their surfaces. While it is possible to make a wine using the wild yeast, a cultured wine yeast will produce a more reliable wine. The sulfite added in the previous step will kill off virtually all of the natural occuring yeast. Wine yeast has a higher sulfite and ethanol tolerance that then wild varieties.