I don't want to be overanxious, but at the same time don't want to miss something that ought to be picked up. My three year old still can't jump at all. She can't jump up and down or off a step or anything. Should I worry, or is this still within normal developmental limits? I did ask the GP about it when she was two and a half, who said she seemed fine and not to worry, she would definitely be doing it by three...