I don't have those but I do have Red Iriani Rainbows,gertrudea, they also flash each other but do leave other tank inhabitants alone. Give them a few days to see if they settle. Rainbows in general I think are quick swimming fish, didn't think the threadfins would start with other fish in the tank. Maybe it's a territorial thing but they did come into an established tank. Gang mentality, they want to take over. I'm sure someone will chime in with more info that might be helpful. Sorry Patrick, hope it works itself out, if not give them a call and see if you can return them if things don't get better.