they were found dead 3 months later. Although they looked like they could just be sleeping, reports show that they have been dead for 3 months. There are no signs of murder/suicide...how did they die?
They had all the equiptment they needed, and I suppose hypothermia COULD be a small part of it....
I think your fish is a Plecostomus, and no...swimming upside down isn't normal. If he's sucking on something & he's upside down, that's pretty normal. But, swimming upside down sounds like he's disoriented. Do you see anything strange on his skin?