https://www.backyardchickens.com/threads/fire-safety-in-your-chicken-coop-barn-important.745178/
mama raised ducklings are defiantly tougher than brooder raised.
Once ducks are completely feathered in and they have a secure house where they will be able to get out of the weather if they want especially at night they shouldn’t need any heat. Give them a generous layer of bedding to snuggle down into they will be good to go.
Two weeks is too young to be out over night, taking them out side on nice warm days for fun would be good though. Mama raised ducks are much hardier than brooder raised.
For one thing week and a half old duckling need to bath in nice warm water most likely the little one got very chilled after bath . After bath they should immediately be placed back into a warm brooder to finish drying with out getting cold. Sounds like you stepped in just in time :welcome...