Ladna is "Fair", but almost always in the sense of fair weather, fair odds, or fair conditions. It's used in the same way as "partly cloudy" in forecasts.
You might be thinking "ładny", which is cute/pretty/nice in a completely innocent way. It's usually a compliment, though i'm not sure if it has the same potential for sexist undertones that "cute" sometimes does in English.
Piękny is better translated as "beautiful", and is much higher praise - a beautiful sunset, your beautiful wife, a beautiful outfit. Like in English, it's VERY rarely used to describe anything seen as stereotypically masculine.
To clarify, it is rarely used about men and "manly" things, but often used to describe things of masculine grammatical gender-ex view, paiting, day, palace, poem, bridge.
also there is no ladna, and ładna, ładny, ładne is the same adjective, different grammatical gender. All the meanings you told are right.