Hibiscus Leaves Turning Yellow

I have two hibiscus plants, one in sun and the other in shade. Several leaves at a time seem to be turning yellow on both plants. Can you give me the cause and cure?

Check soil moisture. Too much and not enough water can cause leaves to yellow. With different light conditions you may be providing too much water for one and not enough for the other. Water thoroughly so the excess runs out of the pot and whenever the top few inches of soil are crumbly and moist. Pour off the excess water. Plants left sitting in a water filled saucer are subject to root rot. This too can lead to root rot and yellowing of the leaves.