What are you water stats as some people say they're fine but they're not? (pH, ammonia, nitrite, nitrate, temp) What are their tank mates? Any symptoms such as flicking, rubbing, listlessness, bloating, etc? The rearranging of the tank may have stressed them out but I doubt it could stress them to the point of death. Did you remove any gravel or leave the filter off for an extended period as you may have killed off some of the beneficial bacteria and the tank went through a mini-cycle. Did you use any chemicals around the tank?
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