"Patrick McDonald" wrote:

Perhaps treat as Negodki recommends but I kind of think it will go away
since it may be a constituent smell because of apple.

I agree, depending on the smell. I've had apple wine smell "vinegary", but
turn out fine. And most ferments with Montrechet yeast will smell a bit
"rotten eggy" for a few days. Hard to tell from here. But if he does have an
H2S problem, it's best to attack it right away.