Hi all, just noticed a bit of unusual behavior by my 2 biggest silver dollars. They have been getting along fine since I added the 2nd one I got from my friend. They are in a 55 Gal bow with 2 smaller silver dollars and some other smaller semi-aggressives. I was away a couple of days and hadn't fed them so I don't know if they might've been pissed at me and were taking it out on each other, but once the food started falling I thought it would stop but even after they both ate quite a bit they still kept knocking their heads into each others sides. Also i've noticed that the one I had originally is missing some of its fins area, so my question is do you think the other big guy is doing it? because none of the other 3 have any signs of fins issues. lastly unfortunately I don't know what sex these are. thanks for any help or suggestions.