Glad all is well and you were on top of checking things.
I lost one fish the night before and two nights before a Bamboo shrimp. Initially I thought the shrimp had been killed after molting as I had seen a exoskeleton a couple days before that. But it seems I have had a mini cycle even after doing what I thought was a gentle cleaning on my FX-5.
This week has been a busy one and I was going to do a pwc on the tank but didn't.
So lesson learned.
Used the Python for draining the water, but I don't have the right size faucet, sink and connector for filling, so it was a lot of work, did a 75% (in the 72G) pwc, added some Cuttlebone powder to help make sure I don't have a pH crash and the fish are looking perkier and I am hoping everything will smooth out. I will be checking the parameters in the morning to make sure all is well. If not will do another pwc.
Pwc in 12G, 6.6G, and snail bucket, and plant bucket and plant bucket 2, and 5G Betta Sorority.