Wild growth is currently completely buged. When cast when pet are present in the group/raid it stop it from spreading to the correct amount of targets. The worst of it all is if by some magic (happen quite often) the primary target is a pet all of the subsequent wild growth do not spread to players.
To make it short as soon as wg touch a pet it stop spreading and it target pets in priority.
If it is not fixed before raids release it will literally kill resto druid as in raids wild growth is extremely important…
Off topic: i have also seen a similar bug with mark. Sometimes it stop from spreading to the appropriate amount of targets if it hit a pet.
No idea how it even posible…it suposed to be all targets…