Answer: Mandevilla winters best in a large pot in a location with full sun such as a conservatory might offer, so it is probably not all that happy in your kitchen. In my experience it is best to keep it as cool and bright as possible with reduced watering and no fertilizing for the winter. (It will eventually lose some leaves and look quite awful in protest, but don't worry.) Promptly remove and destroy any badly spotted leaves. In spring, cut it back, repot and resume watering and fertilizing and set it outside again where it can enjoy lots of sunshine and good air circulation. It should recover to grow and bloom beautifully again.
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