Ok--first thing here is that you don't use sorbate to stop fermentation. Sorbate does not stop it--only slows it WAY down but it WILL continue to ferment until the sugars are used up. But with an SG of what you're reporting, the fermentation IS finished--sorbate does nothing.
If you are doing this because you've been making kit wines, don't continue to use that technique on non-kit wines. Sorbate is added after the wine is clear and ready to bottle--and only if you backsweeten. You have to have most of the yeast cells racked off the wine for sorbate to work. The only thing that stabilizes a wine is bulk aging.
Since you have racked some lees off the wine, the rotten egg smell is H2S which, most often, is due to bad nutrient support of the yeast during fermentation. The yeast becomes stressed and produces alot of H2S. The other reason could be the use of too much sulfite at the primary too. But if you used proper sulfite dose, then it's H2S from stressed yeast.
You will often read about using a copper pipe to get rid of H2S. But doing that puts an unhealthy dose of copper into the wine. Go to
www.MoreWine.com and get yourself some Reduless and dose the wine. This will remove the H2S safely. Do this right away--or else the smell of rotten eggs progresses to tasting it in the wine. And if you don't fix this, then you begin to form mercaptans in the wine.
In the future, always split your nutrient dose into 2 batches. Pitch the first one at the beginning of the ferment, and the second one before you reach the 50% dry stage. Keep your yeast fed, then it won't become stressed.
