Sorry for taking so long to get back, I called a local tank cleaner guy to come by and see what's going on. The Ph was a little lower than it should have been, but the salinity and nitrates were normal (but the nitrates were a little on the high side). He said that the fatty liver disease could be what's wrong. I bought some ghost shrimp today to see if that would coax her into feeding but it hasn't appeared to work yet, the stingray is still doing well.
Other information:
The tank is 3x3x3 I meant to say. It's a big cube that the people at AllFish Emporium told me was "tailor made for sharks".
Also:
I don't have a heater at all, the heat of the pump going combined with the room temperature is 85 degrees on its own. A heater would probably overheat them.
I'm a bit nervous to answer that, just out of standard internet precautions. Nothing personal, its just I'm very cautious to trust anyone online.