Possible Cause: Poor lighting conditions.

Management: Most indoor plants need an average of 14 hours of sunlight each day. Do an Internet search to find out the proper amount of direct light, indirect light, or shade that your particular plant requires to thrive.

Possible Cause: Too much nitrogen fertilizer.

Management: Most indoor plants need to be fertilized just once a month and even less frequently during colder months. Develop a fertilizing schedule and stick to it.

Possible Causes: Overwatering, low humidity, poor soil drainage, low temperatures, or pot-bound roots.

Management: If the weather has changed suddenly, make sure that your plant is not in a draft, near a heater, or reacting to an unexpected environmental change. Check that your pot has adequate drainage and that the plant isn't root bound.

Possible Cause: Too much direct sunlight.

Management: Move plant from direct to indirect sunlight, prune the affected leaves, and resume deep, infrequent waterings to promote healthy root growth. Avoid overfertilizing, as this will exacerbate the burn.

Possible Causes: Too much fertilizer or pesticides, dry soil, low temperature, hot air, accumulated salts, or root rot.

Management: It bears repeating—most indoor plants need to be fertilized only once a month, at most. Stand pots in shallow, pebble-lined trays that are filled with water to increase humidity (pots should sit on the pebbles, above the water line). Once a month, apply enough water to the top of the soil to thoroughly flush excess salts through the drainage hole.

Possible Causes: Soil remains either too wet or too dry.

Management: Develop a watering routine that is infrequent but deep to promote healthy root growth and combat root rot. If root rot is suspected, remove the plant from its container, examine the root system, and cut out infected roots (blackened root tips with slimy decay), then repot using sterile potting mix and a clean pot.

Possible Causes: Fungal leaf spot, water spots.

Management: If the plant is already affected, isolate it from other plants and pick off infected leaves. To prevent spotting, increase air circulation by increasing space between plants, and take care not to splash water on leaves when watering.

Disease: Anthracnose.

Management: Remove infected leaves. Avoid misting leaves.

Disease: Powdery mildew.

Management: Increase air circulation around plant and remove infected foliage.

Possible Causes: Root and stem rot.

Management: Avoid overwatering. Remove affected plant, cut out infected roots (blackened root tips with slimy decay), then repot using sterile potting mix and a clean pot.

Disease: Botrytis blight.

Management: Isolate the diseased plant and trim the affected parts back. Increase air circulation by increasing space between plants.

If you are interested in more about indoor plants, consider:

10 Houseplants to Improve Indoor Air Quality

Breathe Easier at Home with Indoor Plants

5 (Nearly) Kill-Proof Houseplants