If you know the Comets are giving soft eggs, can you give them whole calcium tablets in their beaks? When you dissolve them like that, they can't get the whole dose unless they eat the entire mash you dissolve them in. Just take them off the roost at night when they are calm and easy to catch, pull down on their wattles to open their beak, and pop the tablet in. They can swallow it easily although it looks big. They can swallow a whole mouse! Do this every night for a week and your problem should be solved.