Action Triggers

Two questions.

Are there triggers that can make a group of units within a range of a unit decrease in scaling value? Also is there a action trigger to add buffs cause I saw the one to remove them but not add them?

You'll want to apply the "Animation - Change scaling value" and "Unit Group - Pick all units in Group and do actions" actions, with the "Units within radius" function.

The only way I know of to add buffs to a unit is by having another unit cast an ability on it that produces that buff.