Bala Shark Behavior

I hope I posted this in the right section. If not, then please move this to where it should be.

I have 3 Bala Sharks with other tankmates in a 150 gallon tank. 2 of the Bala Sharks have been bumping into each other, rubbing scales and basically harrasing the heck out of each other. It has gotten to the point where both Balas have torn fins. The two Balas in question pay no attention to the third Bala or the other tankmates. This behavior has been going on for over 3 weeks now.

Anyone have any idea what has gotten into these 2 Bala Sharks?

BTW, they are approx 4-5 inches in length.

Thanks.

Anyone experienced the same behavior? Does anyone know why they are behaving this way? I haven't been able to find anything about this on the internet.