I ond't think for a minute that you had anything to do with why he keeled over. He wasn't in your care long enough!!! One thing I do recall is that there is no way that he can starve to death and there is no way that the temp was too hot or too cold (heck they live all over the US!) He could not have dehydrated and there is no disease that is native to turtles that he could have caught and gotten so advanced as to cause his demise! (Translation= You didn't do it)

God bless!