Answer: If the leaves on all your houseplants are turning yellow, it could be that they are all shedding the oldest leaves in preparation for developing new leaves. It could also be that you're dealing with an insect problem, especially if the plants are all grouped together. You might want to carefully inspect each plant, especially the undersides of the leaves and where the leaves meet the stems. Look for insects or other signs such as webbing. Once you've ruled out any insect problems, the problem might be with your watering techniques. Plants in containers can develop air pockets within the root mass and no matter how much water you apply, it just drains through without wetting all the soil. To overcome this problem, periodically set the plants in a larger container of water and let them sit for about 15 minutes, or until no air bubbles rise to the surface. Then set them in the sink and allow them to drain. As for the largest plant, I'd set a saucer beneath it to catch the extra water. If you immerse the plants in a container of water every 10-14 days, the soil should expand and absorb moisture each time you water instead of letting the water simply drain through quickly.
Hope this information helps!
Q&A Library Searching Tips