Are 3 week old chicks old enough to given treats other than boiled egg (which they like) and yoghurt (which they don't). Would like to use treats to make them friendly to see humans, as suggested here. Know from our dog the power of treats! Are they also old enough for grit now - and do they only get it with food that needs it? Any harm in giving it to them if they are not eating insects, greens etc?