Hi.
Do they do this if you watch them from the other side of the room? If not, then I think it may be that they get spooked when you get too close for their comfort. I find from personal experience that the fish you raise are much more calm, and in my case will actually swim over to your hand where as fish from a pet store have had to deal with many people's hands and may find them to be stressful.
You say you've had them for only a few months, so maybe they need a little more time to adjust to their new surroundings. I think in a few more months they will remind you of your other oscars and "greet" you when you come by.
Also, do you walk kind of slow up to their tank? Perhaps if you walk slower towards them they might not feel threatened. Just suggestions... let me know if they work.
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Phishie

"An ounce of prevention is worth a pound of cure."