Bite wounds or something else?

[Truth]

I've got an aggressive tank I keep, one of the eels a yellowbar moray died a few weeks ago from similar looking marks now on my grouper, I thought and think it's bite wounds from the large tang I keep who's pretty aggressive or maybe the insulate trigger who's very territorial but someone suggested I run it by you guys with pics just in case it's something worse

Sorry for the bad lighting,please let me know what this is