i looked in the tank and two of my frogs were dead with one of their feet behind them like they were stretching out or something and i took the remaining 3 out and they seemed fine but one of them is dying now what could make them die one after the other ...i just changed the water after the other two ..i think maybe it was the last wax worms i fed them?? is there anything i can do to give the others more of a chance?