@CDrew raised a critical point -- loss of wine during racking. Every time a wine is racked, volume is lost, so this is among the reasons to rack a wine as few times as feasible. I made a list of things I do to reduce wine loss during racking.
But if you ran these numbers the day after crushing (as opposed to day of previously), it could also be due to 'soaking up' - Grapes release sugars, potassium amongst other things (particularly since you added macerating enzymes) which can cause brix to rise and acid to fall. (You didn't post revised brix numbers and it's probably too late if your ferment has started, but I would imagine it also went up.) See my recent numbers for my 2023 syrah for another example.
: nod: the musts sat for about 16 hours between samples and i didn't see any activity — i pre-chilled my grapes with chips of dry ice in the bin as i was picking and iced the outside of the bins down during transport. the must was quite cold out of the press and took overnight to warm to 65. I did sample brix again and saw no change in that time. fermentation is picking up nicely in the primitivo (was corrected which one they grow!) now, but still a little cold, working on getting the musts up to 70.
will definitely treat those initial readings as suspect!
: nod: it's the same with the barleywine — i get something like 7.5 gallons into the primary fermentor for a bit under 5 gallons of finished beer. it's just as heartbreaking as thinning fruit in early summer, you *know* it's worth the end result but it still hurts!
with brewing i normally ferment and age in corny kegs under a spunding valve to totally inert the keg atmosphere, with the wine i'd been planning on transferring to a keg for secondary and filling the airspace with nitrogen to keep the seal. I've got a couple of the little 3-gallon size ones that should minimize headspace issues for the small batches — if possible i really want to keep the wines separate to have a little redundancy if i make a critical mistake.
small update — i racked the wines off the gross lees tonight, they're definitely done fermenting — i won't have a chance to re-run the labs til after thanksgiving, but my palate says they're nice and dry.
it's been quite educational to taste reds that haven't done a MLF yet, i can clearly taste the MA's appley sourness that doesn't belong in a red. they definitely need oak too, picked up a couple american medium toast spirals for that. can't wait to try it after!