If the Deal action has multiple targets, the amount of Damage dealt to each target is increased by Bonus Damage individually and separately. Example: Singularity is a spell that says “Deal 6 to each of up to two units.” A player plays Singularity while they also control Annie, Fiery, a unit that says “Your spells and abilities deal 1 Bonus Damage.” Singularity deals 1 Bonus Damage to both of its targets, dealing 7 to each.
§ 715.2 Core Rules PDF (officieel)
§ 715 Bonus Damage applies to the total damage Dealt by one instance of the action.
