New test kit came in. Ph 6.6, ammonia 0, nitrite 0, nitrate 10. Picking up a hardness test this weekend. Clearly my water is not as hard as i thought.
Based on the tank still being fully cycled, I'm hesitant to think the cycle actually crashed. There'd be signs of ammonia or nitrite. If it stalled, there'd be signs of them or higher nitrates.
Thinking back I recall seeing a red spot with slightly scales on her back a few days before her passing. It healed completely in 2 days so I thought nothing of it, maybe just a scrape from jumping. But now I'm thinking it might have been more than that.