If a battery was full of electrolyte and electrically disconnected for eight months and not kept in a very hot environment
and is has lost
a lot of electrolyte, I can only see a leak as the only option.
Now were they all connected together, and were they all dead as doornails? If so , well then maybe one shorted battery discharged them all, heating
up in the process and boiling out the electrolyte?
I have seen a battery or two in my life leak, but they had been dropped and had obvious cracks in the case and if you missed that, you couldn't miss all the leaking electrolyte