I was thinking originally, could crabby's torts have food on them, like blood,mazuri banana or strawberry juice(anything they go mad for) to cause the biting at each other. That's why I said just feed dandies and mushrooms to eradicate that theory.
Then........
Could it be a redfoots natural instinct/need for animal protein kicking in, if the need is not met, they turn on each other. If they were my torts I would feed them 2 or 3 pinkies each(just as a one off may be) then wash the torts and see what happens over the next few days. I would try everytjing possible before deciding to get rid of some, must be an answer. Horrible situation to be in.
Like zombie tortoise....uuuuhhhhhhhh (that was zombie tortoise sound) uhhhhhhhh