sand-sifting goby

Hey guys, My Bella Goby is suddenly extremely off and looks like a goner - her mouth is stuck open and gills are not moving. She was fine this morning and was eating with everyone else. Params all check out - sal at 36 PSU, 8.2 pH, 25c; alk’s at 8.4, nitrates at 5ppm, phosphates at 0.07. Any...