Why are my indoor plants getting yellow leaves?
There can be numerous causes for leaf yellowing of houseplants. There is always a degree of environmental shock when plants are brought indoors for the winter and this can cause the malady. And, true, over- or under-watering can have the same effect. Typically, houseplants want to rest in the winter, so over-watering can cause them to yellow. On the other hand, the change in humidity can have a similar effect. It may be appropriate for you to either mist your plants occasionally or provide them with a humidifier. A simple method is to place the plants on trays that have a layer of pebbles on the tray. Keep just enough water in the trays to stay beneath the top of the pebbles and avoid allowing the bottom of the plant's container/pot to touch the water. The evaporation of the water will provide a good amount of humidity to the plants.
Avoid placing the plants in a draft, either a cold draft or a warm draft.
Be sure to examine your plants carefully for any insects such as mites or scale insects.
Your houseplants should recover as they re-adapt to the indoor conditions, but sometimes it is necessary to modify those indoor conditions.