My 12 week old pullet is on start and grow chick food and they said to put her on it until 20+weeks. She's is not on any vitamins or anything, when do i move her to grown up food?and also i only have 2 chicks so there pets, she's not flock so what kind of start and grow next? i also heard your supposed to put gravel in her food to make her shells harder.is this true? and if so her and the roo share food, is it ok for him? also what kind of gravel? and when do i start giving it to her? thanx i need all of these questions anwsered.