Whats happening to my clowns tail?

So it started with my cardinal, where it had its tail torn off or eaten off I'm not sure, but it passed way 2 days later, now my little clownfish (most likely male since its smaller than my other clown) has his tail torn off, what the heck is happening? is it a disease, or are they mating roughly or whats happening?

Nitrate-40
Nitrite- 0
ammonia0.5
ph-7.3
temp~78
Livestock:
2 clowns
1 McCosker wrasse
1 filefish goby
1 watchman goby
1 pgmy filefish
BTA
cleaner shrimp
peppermint shrimp
camel shrimp
fire shrimp
decorator crab
tiger pistol shrimp ?

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