Focus on light, water, and humidity.
Adjust lighting. Place plants near south- or west-facing windows to maximize limited sunlight, or use grow lights if natural light is insufficient.
Water less frequently, as most plants grow slower in winter, but ensure the soil doesn't dry out completely. Stop fertilizing.
Increase humidity by misting plants, grouping them, or using a humidifier to combat dry indoor air. Keep plants away from drafts, radiators, and heat vents to prevent stress.
Dust leaves to allow better light absorption, and avoid fertilizing until spring when growth resumes.
Check for pests.
Check temperatures.
This article provides excellent details on all of the above.