I can't help but think that there's another player here. Even if the Sparkhounds are smart enough to recognize Agatha and Violetta and follow an "ignore these people" order, why would Tweedle have them go after Smoke Knights?
He just got done recruiting a bunch of them. Sure, I'd buy that there could be more in the castle that aren't listening to Tweedle, but sending out Sparkhounds to hunt Smoke Knights when he's actively using Smoke Knights to hunt Agatha seems like a terrible waste of resources, even for an angry spark.