Adjust the amount of light your orchid is getting. Yellowing or black-spotting of orchid leaves could be an indication the plant is getting too much sun. Place the plant behind window blinds or shades, and cut the amount of full sun it receives by half.
Increase the amount of plant food you are feeding your orchid. Dying leaves are potentially associated with poor nutrition. Add an additional teaspoon of plant food when watering, to see if the leaves return to a healthy state.
Use a water testing kit to check the hardness level of your water. The blackening of orchid leaf tips could be an indication of hard water. Use bottled or purified water, if necessary. Prune the black tips with pruning shears to prevent any spreading.
Maintain a constant temperature for your orchid plant. Temperatures that are too cold or too warm can cause the plant to wither. For best results, keep the ambient temperature at night in the range of 60 to 65 degrees Fahrenheit, and keep it 75 to 85 degrees during the day.