Answer: Both bougainvillea and mandevilla like heat and lots of sunshine so the lack of heat might be what's ailing your plants. You'll also want to take into consideration the time it takes plants to acclimate to a new environment. If you only recently moved your plants indoors it may take them several weeks to adjust to the changes in temperature and humidity they are experiencing now that they are indoors. All of your plants are tropical or sub-tropical in nature; they'll appreciate lots of light, warmth and a fair amount of humidity (something that's often lacking when we're running the heating unit). You might try running a humidifier in the room or setting a tray of water near the plants. As the water evaporates it will increase the humidity near the plants.
Best wishes with your indoor tropical garden!
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