2005 ISX

About a week ago I realized my truck would take 2-4 tries before it would start. Today, after shutting off the engine, I tried the key again and it won’t crank. Tried again 2 more times until I heard a small explosion. Two of the batteries burst open at the terminals. Checks later reveal that the third battery ground cable was broken which was hard to see because the break is under the black rubber coating. Could this been the no start issue that I was experiencing before?

Alternator was cleaned and starter replaced two months ago. Batteries are about threemonths old which all will have to be replacednow.