I’m glad you’re using an ML nutrient (Opti’Malo Plus™ — made by Lallemand and sold through various outlets like Scott Labs and many home winemaking stores), which makes for the most predictable and successful results. I must admit, I’m a little old school when it comes to malolactic fermentation, but it’s always served me well. There are some winemakers who try to get a jump on ML completion and co-inoculate ML bacteria and wine yeast at the same time, but in my mind this is a little risky.
You see, yeast and bacteria actually “talk” to each other during fermentation and sometimes they don’t like what they hear. In fact, when I was just getting my start as a winemaker in California, I read a really interesting paper published by Dr. Linda Bisson’s lab at UC-Davis showing how wine bacteria “query” the environment to check for competitors and adjust their metabolic process accordingly. Too many mixed messages in some cases can cause problems with fermentation completion, higher volatile acidity, and other non-optimal outcomes.
The take-away for me is that I like to let the yeast do their job eating sugar first (and making carbon dioxide and ethanol) undisturbed by too many outside competitors. Once they die off after primary fermentation (and the fermentation is hopefully dry), I press off my new wine and immediately add my ML bacteria and any ML nutrients together at the same time to the container holding the new wine. If you add your ML bacteria and ML nutrients before pressing off, you’ll lose a lot of the dose (and those additives are expensive!) in the skins that get discarded. Also, once you have the wine separated from the skins, you know how much wine volume you have so you can measure your bacteria and nutrients accurately. It’s hard to tell your final liquid yield when the wine is still sitting on the skins.
I would add your ML bugs and nutrients evenly into your carboys right away after pressing and racking into the containers. This way you can also take advantage of any residual warmth carried over from the primary fermentation. I really like that you are using ML nutrients; that, in addition to the heat, will really help your ML fermentations get off to a great start!