Vic cotroni has been dead since 1984.
There hasn't been an influential cotroni in MTL since the death of Frank cotroni in 2004.
As per the conflicts in the past 17 years it will take time to figure out who is fighting whom. What is clear from reading the source book about scoppa is that the MTL mafia and OC groups in general are extremely cut throat and loyalties from the past mean nothing.
Armeni and del balso have no connection that I know of for working together.
And can think of no reason why they would be at odds.
As another post stated maybe it was the nuns.

The conflicts in MTL cannot be so easily explained as a Sicilian vs Calabrian war.
I don't even know what part of Italy del balsos family hails from and in this context it doesn't matter. He's a prominent criminal in a hyper criminal city I'm surprised more it took this long for someone to take a pot shot at him.