Yea, I try to tell them to go to treated tap water but she's always done distilled.

I told her it's hard to figure a way that the wafers could start something, but it's the timing of the outbreak of whatever is wrong.. maybe algae wafers can't be put in distilled water - they certainly look VERY different than wafers left in treated tap water. The one cory cat who died did seem to be seperate from the others & smaller.. i wonder if he had something the other fish caught - but then i don't know why Sora and the other 3 corys would be fine.. kind of a mystery.