Think about your new clowns as being in an ocean where they don't see any other fish. This is a disturbing situation in the ocean and it means that there are predators around so stay hidden. Once you get a few more fish in the tank they should become more active and not just hanging out at the top corners.
As far as the picking on the other that is going to happen a lot until and even after they have paired up. My Mocha Ocellaris pair constantly fight even though one is clearly the female and the other male. So don't worry about them fighting, it's to decide dominance and who will become female.
So start thinking about your next fish addition, you're pretty safe adding a fish every two weeks allowing the bacteria enough time to grow to handle the additional load. I would not add anymore than two fish at a time as you could end up with ammonia problems until the bacteria has grown to handle the new load on it.
+1 when I upgraded and transferred my clowns over, they were the only ones in the tank for a while and hung out in one spot. Once more fish were added they started moving around quite a bit.
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