Can someone please help explain how one goes about proccing the battles for Voidwatch Provenance.

Specifically trying to Proc white (or whatever helps to get the dusky periapt)

I never had to learn how to proc the earlier battles since when the campaign is on, the white light is 100% until you reach provenance (the final 3 battles before the watcher).

I don't seem to have problems killing the mobs, but they never drop the key items and I know for sure its because i'm not proccing the mobs.

I've found numerous posts on instances saying it could be ability/magic/etc but I still don't understand how to work out which? I'm also doing it solo with trusts as I don't know anyone that has bothered climbing any higher than Aelo so they can farm heavy metal plates XD..

Thanks,