Almost positive that your rotten egg problem is due to the yeast, and most specifically the temperature in which the yeast is fermented. Depending on the type of wine (I haven't had this problem with wine, but I have with beer) some don't follow the conventional temperature guidelines as others.
I had this problem most often when I was brewing lager, which requires fermenting at the lower end of the yeast temperature range.
One other possibility is simply the strain of yeast that you used. Some yeast will simply reek of sulfur even in the secondary. This smell may simply go away once the process is finished, it really just depends.