How big is your tank? Scooters are dragonets just like mandarins, in other words they have special needs for feeding. Unless your tank is 90G+ with a sump, having 2 in the same tank is a bad idea due to the need of pods
which they munch on constantly. My guess is that they may have starved unless you had them trained to a prepared food. Many people don't know what they are getting themselves into when they bring a member of the dragonet family home. As for the mandarin, hold off on that idea unless you can get you hands on an ORA mandarin which still have reports of them going back to pods
after being added to a tank.