Yesterday I did a 50% w/c. Readings were pH = 7.6, Ammonia = .25, Nitrite - .5, Nitrate = 10 before w/c. While doing some aquascaping I noticed one of my F Bettas was very beat up (the newer one I got). I had noticed the M would chase her around a bit; never saw him do more than chase her for half the length of the tank and it was every once in a while since I put her in. I thought just because she was new and he was trying to show his dominance. But when I saw her yesterday.... all her fins were tore up. Like they were nipped. She was always chilling under the lag I have in there, so I didn't notice it until I took that out. None of my other fish have this issue.... not even my other F Betta. So I took her out and threw her in my 1.5g so she can heal. Redid everything and that was that. Everyone was doing fine. I woke up this morning and she was doing fine. But when I went to turn on my lights for the 72g.... My M Betta was dead. Because I was running a bit late already and in uniform (Navy) I didn't have the time to fish him out. I figured I'd do that first thing when I got home and test my waters.... When I went to my 1.5g.... my F was also dead. I asked my wife and she said that when she got home from being out.... she was still alive.... so she had died in about the last 2 hours since I got home. My M Betta was half eaten.... and my Ghost Shrimp were already starting on my F in the 1.5g. So I did my readings using the API Master FW kit.... 1.5g - pH = 7.6, Ammonia = 0, Nitrite = .25, Nitrate = 10. 72g - pH = 7.6, Ammonia = 0, Nitrite = 1.0, Nitrate = 10. Should I do another water change? Should I wait to redo my readings tomorrow? Please give me some advice.... I know the Nitrite in my 72g is the highest I would want it to be. Can I wait till tomorrow and see what happens? Everyone else in there seems to be fine.... My Crayfish did his first shed. All the free guys I got where but in Th of last week. Thanks again for all the help.