I think that the Mob spawners: (the Single-, Multi- & Zone Spawners) should have an extra Input that's blue.
And that the Effect/Potion Infuser gets an extra Output that's also blue.
these two will connect with eachother and the effect from the Effect/Potion Infuser will be given to the Mobs from that Spawner.
Heres a list of what the effects will do to the mobs: