Hydrogen Sulphide in Primary

Some yeasts produce H2S during fermentation...this could be what's happening. You could pour the fermenting wine from one container to another giving the wine lots of air. That should help the yeast and also get rid of the odor. Perhaps another DAP dose...1 gram/gallon based on juice volume.

Bill Frazier Olathe, Kansas USA

I would go to the local drugstore and buy a small bottle of pantothenic acid (a vitamin) and I would add about half a tablet to the stinky fermentation. Lum Del Mar, California, USA

Here's a link that mentions shortage of nitrogen and pantothenic acid in connection with hydrogen sulfide contamination.

Montrachet yeast is notorious for causing H2S.

Other causes can be too much sulfites, usually the result of grapes being dusted with too much sulfur during the growing season;

or bacterial contamination due to poor sanitation techniques..

Link goes into more detail..

Good luck..

fermentation.

Forgot the link, now didn't I. Here it is.. sorry about that..