Mine swims up and down the glass when she is hungry, however, I've had her for 4+ years and she knows how to get my attention. I'f I'm correct, yours are still babies, so they wouldn't be doing this becuase of that. They are either insecure, trying to swim past thier reflections, or are still just getting used to the tank. I wouldn't really worry about it unless they're still doing it in a couple weeks.