I did forget to mention the behavior you were seeing before they
spawned is very typical of Angels before they settle down to spawn.
They are doing a mock battle. This is a way for each of them to see
whether or not the other is (or still) worthy of spawning.
Many pairs will do this just like if it were the first time. Some may
settle on a little fin flashing, some a lip lock-tug o war (this looks
so painful), some just keep intruders at bay and then just spawn.
I currently have 2 males bickering over the same female. She shows
interest in them both, yet neither will back down. The males do a lot
of fin flashing and nipping here and there, but don't do any damage to
each other. It's more for the point of showing off to each other than a
true fight.
I have left them to figure this out on their own, unless it gets
nasty.