Is a prospective bride obligated to inform her fiancé about a slight deviation in her spine and black spots on her leg, and would her silence about this be considered deceit?

Do not destroy yourself with stress and anxiety, and entrust your affair to Allah the Almighty. These flaws you mentioned are not among those that must be disclosed to a suitor, for they are minor and usually do not repel a man. Therefore, you are not obligated to inform him of them, and this is not considered deception, because marriage is built upon forgiveness.