I got a call this evening from a very good friend, her voice I could hardly recognize as she way crying so hard. She had just lost 4 large tangs that she has had for nearly 10 years. I raced to her home with a volt meter and other testing equipment to find nothing out of normal. The only thing she did today was a weekly water change. She normally keeps salinity at 1.024 - 1.025. I read it to be 1.029. Would that swing be enough to kill 4 otherwise healthy fish?