I didnt see what happened exactly but i think my young gold spot rabbitfish killed my slightly larger one spot foxface. they would usually fight over nori with my foxface bullying, nipping at the smaller rabbit. as the gold spot rabbitfish grew larger, to match the foxface in size, the fighting seemed to slow down. this morning, both rabbitfish were healthy and swam to get the nori i put in. a few hours later, I find the foxface dead on the bottom. again, not sure what happened, but I assume the foxface was bullying the gold-spot for taking most of the nori, and the one-spot put up his spines in defense. i would see similar displays often between the two, but i think this time the foxface got spiked. i dont know if thats what happened, or if the spine attack alone could kill the foxface, but it seems like it. other fish are fine and the water is fine.