projectile damage nodes work on secondary effect?

I feel like i am a bit falling behind in terms of damage on my build ( ranger focusing on lightning arrows) so i was thinking to grab all the nodes nearby with "+x% increase in projectile damage".

does this damage apply to the chain effect of lightning arrow or just on the "first arrow"? what about on the delayed lightning of "stormcaller arrow" is that a projectile too or does it buff only the initial arrow?