post mortem nibbles are usually first made in the belly and eyes. Attacks are found on the fleshy part of the body... IMHO


however, while rereading the post, i noticed the Ph drop. do you have any driftwood in the tank or any chemical altering Ph? if not, something else must have dropped the Ph.

perhaps there Was an ammonia spike (ammonia lowers Ph), that killed the fish, and dropped the Ph, then after fish loss the ammonia cleared up but the Ph was slower to return to normal.

is the Ph normal now?

the only thing that doesn't fit the ammonia spike idea is the loss of the female bettas. they should have been the last to go for that reason

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Gold Coast Aquarium Society South Florida