I suspect your batteries have sulphated and are toast. But following the recovery procedure you might get some capacity back, in some if not all of them. Most people are aware that chronic undercharging leads to sulphation. Less common is sulphation from keeping fully charged, but not cycling the batteries.
How I came to discover this phenomenon..... 1700Ah of batteries only 15months old..... was due to looking after an ill family member 4000km away. I did not use my boat for 5 months. Victron charger set with "storage" function at 13.2V, and solar to keep charged, 13.5V float, if I lost shore power, kept the batteries fully charged. Sweet, or so I thought. But deep cycle batteries need to be cycled. Just how much and how often is not clear, but they do not like sitting at full charge without cycling.
In your post you said "first trip out in almost a year". To me that was the give-away. I'm told that some brands of batteries are more susceptible to this failure mode than others, and think Lifeline would be one of the better brands. You might recover some, or some capacity. I've just installed 900Ah of LFP.