Just a slight sulfur odor appeared on day 3 primary fermenting my Winexpert Eclipse Stags Leap Merlot. I had made three tweaks from what came in the kit: used RC-212 yeast instead of the supplied EC-1118; put only one half of the supplied oak sawdust in, but put it in a nylon brewers bag with the supplied grape pack, plus about half a gallon of Pinot Noir pomace from a pressing of frozen must I had made last week (and frozen the pomace immediately). I started with supplied bentonite as recommended, although what a clumpy mess, next time I might dissolve it in a blender. The Pinot Noir pomace had been fermented with Assmanhaussen yeast, co-inoculated with White Labs liquid MLF at Brix 5 as they recommend. I wonder whether I co-inoculated this ferment with either or both of the yeast and/or MLF through the pomace, which had only been in the freezer until it was gelled, not frozen solid. Starting SG 1.10, the ferment was active pretty quickly, incredibly jammy, fruity smelling on days 1 and 2 after pitching ... but on day 3 at about 1.07 SG a definite sulfur smell, not overpowering but there. I did a few things immediately: 1. Fed Fermaid K in two small feedings about 18 hours apart, at half the recommended rate, the second at SG 1.05; turned down the temperature in the room from 72 to 69 (the ferment looked a little overactive and the bag of grape skins was holding in heat - it was hovering just around the low 80’s), 3. Decided the pomace experiment might not be helping in the bag having so much mass, not gassing the sulfur I could smell in it and also holding down heat and gassing-off, so removed it and pressed, then threw in some oak cubes. 4. Sanitized a small pitcher and gave the fermenting juice a few minutes of dipping and pour back to try and aerate it somewhat. Now on day 5, still a very slight sulfur smell, slower ferment, SG down to 1.03, temp 76. I intend to bulk age with oak cubes for a couple of months, will probably skip the sorbate but when the primary stalls out at an appropriate SG below .997 will treat with Kmeta and follow the prescribed fining/clearing/racking recommendation. Have read as much as a I could find on H2S. Seems to me I have taken the initial steps to try and get a handle on it, now best to wait even though the slight sulfur smell is still there, until I rack to secondary and treat with Kmeta, after which I can decide if copper, or reduless, or other steps are required. I know there is always a risk of mercaptans forming, and the batch being faulted beyond recovery. On the other hand, others have often cured H2S in secondary successfully. What I don’t know or have sufficient winemaking experience to judge is whether I am getting in a knot over some innocuous H2S gassing off during primary that isn’t that unusual and will just pass. Or whether I should be taking more aggressive counter-measures sooner. I had a prior H2S problem in another red wine ferment with too much heat and leaving the gross lees too long and that wine is probably unrecoverable although I set some aside to see what age does to it after going through some of the more drastic copper steps - it really stank at its worst. This is a fraction as much, although much earlier in primary. Any experience/thoughts appreciated. And yes, I know by chucking that pomace in there I was into uncharted territory and might have stressed out the yeast and the kit-designed balance for fermenting, that coupling that with using RC-212 instead of the EC-1118, and potentially starting a co-ferment with MLF might have played into that. Just trying to crayon outside the lines?