What was your starting gravity? Its possible the majority of the fermentation occurred quickly and now the yeast are just cleaning up. Its hard to see what's going on because your using buckets. You had airlock activity so I think its okay. Push down on the bucket lid and see if the airlock bubbles. If so, then its fermenting.
You can make beer without a starter; a starter helps the yeast do a better job of fermenting. I think a pack of Wyeast is supposed to ferment 5 gallons up to a SG of 1.056 without a starter.
Beer is proof god loves us and wants us to be happy-Franklin