You could also lose alcohol to heads and tails. If your fermentation tem is too low it will make lots of tails. You wouldn't bother to collect them but it is technically alcohol and all analog measurement methods account for all types of alcohol.
I've had many clients from the wine, beer or cider industry not understand that most of the alcohol they make comes through as tails to us. I've even seen as low as 10% yield because the "Fermentation Scientist" wouldn't let it ferment warm enough.
Also, definitely adjust the pH before and during. Minutely, but keep the yeast comfortable.