My Mystery Snail started off completley fine. Moving around, eating algae. Then one day, I look at my tank, an see my snail, all gray. The snail is not in the shell, it is not moving, and I see no antennas. I am about 95% sure it is dead. Now, I also have another Mystery Snail. It has just disappeared. My guess is that it is hiding or something, but then again it probably would not matter because the ammonia for the death of the other snail probably would have killed it anyway. I am at loss of what to do. Should I do a 100% water change? I am adding a new fish to the same tank.