If the plants you brought in from the garden to overwinter aren't looking as healthy as they should, check out this list of problems and solutions to see if you can remedy the issue.
Problem: Weak, leggy plants
Cause: Lack of sunlight
Solution: Find a sunny spot by a window, away from forced air vents. Pinch back to two healthy leaves to increase fullness.
Problem: Lack of good natural sunlight
Cause: Window faces north or east
Solution: Supplement natural light with a fluorescent grow light.
Problem: Spindly, leggy stems
Cause: Low winter light levels
Solution: In mid-winter decrease the heat slightly, and water less.
Problem: Leaf drop
Solution: Acclimatize your plants slowly by moving them into the shade for a few weeks before bringing them indoors.
Problem: One-sided growth
Cause: Light from one side only
Solution: Turn your pots ocasionally to encourage 360° growth.
Problem: Soft growth
Cause: Too much fertilizer
Solution: Avoid fertilizing during the winter as this encourages soft growth, which is more susceptible to pests and diseases.
Problem: Yellowing leaves
Cause: Possible overwatering
Solution: Dehydrating wind isn't a factor indoors, so water less than you would outdoors. The soil should be just moist-not too wet.
Problem: Failing plants
Solution: Maintain good airflow and don't crowd plants too closely together.
Problem: Spots on the stem or on the roots, plus wilting
Cause: Possible stem rot, crown rot or root rot
Solution: Check to make sure soil drainage is good, and reduce watering.
Problem: Evidence of pests, i.e., webs, etc.
Cause: Aphids, spider mites or white flies
Solution: Wash plants and pots with insecticidal soap before bringing them indoors.
Problem: Brown, wilted leaves
Cause: Dehydration, overwatering (the symptoms are the same)
Solution: Buy an inexpensive water meter at a garden centre to be sure. In the average Canadian house in winter, when light levels are low and you aren't feeding plants, their growth is almost stopped; watering once a week should be quite sufficient for most types of plants.