What would cause the leaves to turn yellow?
My Hibiscus Plants That I Have in Containers.
Certified GKH Gardening Expert
There are many things that will cause this in container. If they are indoors, then chances are the humidity is very low. This will signal them into dormancy. This can also be caused by a lack of nutrients if you do not fertilize at least once per year.
Unfortunately this can also be caused by a lack of light, Too little or too much watering, and many pests. Could you include a picture, some more information about your area, climate zone, etc? Also pictures can help here as well.