No ammonia spike and no carbon......she is one of two original Cory's I got about six months ago. I added two more about three months ago and unfortunately didn't quarantine, kinda new at this aquarium stuff. They both were pretty wimpy when I added them. Within two weeks they died. My male started flashing I started treating with paracleanse round one and he did the same thing flashing on day five of the treatment. Two days before round two he was eating, swimming, seemed okay then the next hour he was laying upside down , mouth wide open and dead. My remaining girl started flashing The next-day. I started round two of paracleanse then. I don't know what else it could be. I wish I knew. Thanks for the advice. All other fish are eating great, active and not flashing.