Arc Witch with On Hit Abilities

If Arc Crits the first enemy does it crit all the others as well? Or is it each chain has a difference opportunity to crit?

Does the same thing apply to health leech? Will it Proc on each enemy hit or only the first one?

Also with shock chance say is it each enemy hit has a difference chance to proc shock? Or If you shock the first enemy all the rest are shocked as well?

Arc and most other spells are "all or nothing" in terms of crit. Meaning it rolls for crit once each cast, and if you successfully get a crit, every single chain will crit.

Life leech procs off every single enemy you hit, but you only get the life leech from the single highest damage hit you dealt. You can only have one instance of leech going at any given time. Vaal pact makes leech apply instantly, meaning you get ALL of the leech from every single enemy you hit instantly, but you only get 40% of that healing.

As for chance to shock, I am actually not too sure about how it functions with arc so I might be wrong, but my hunch would be that it rolls for each enemy separately.