Can anyone tell what pickups were used on the Aria Pro II SL Series guitars like the ST SL-3 models?

Hey, welcome to the Forum, R.T.!

Uhmmn, I really don't know what they used, probably not any particular name-brand pickup "specialist" like Seymour Duncan or Dimarzio, or they'd use that as a selling point in their ads for those models and you wouldn't need to ask!

I'd say, if you like their sound, fine; if you like the guitars, but feel there's something either lacking or in need of a change in the sound of the pickups, then they're easily swapped-out for something more specifically suitable.