I came home to find my black molly floating at the top of my tank, lifeless and discolored. She was in a 55 gallon community, stocked with other livebearers, a couple angels, and some bottom feeders. Parameters were 0ppm ammonia, 0ppm nitrite, 40ppm nitrate but my pH that is typically 8.2 (it is high but I haven't ever had issues) has jumped between 8.4-8.8. This tank is 8 months old and the molly was one of the first fish I stocked in it along with another molly that I lost at the beginning. She didnt seem to be acting strange or sick. Anyone know why this happened?