We moved into a new house in SW FL (the Cape Coral area) a couple of months ago, and the front was landscaped with 5 hibiscus plants. All of them are flowering nicely (a nice, fuchsia color), but 2 of the plants have begun to have more and more yellow leaves. They all have gotten the same fertilizer, and get the same amount of water from the irrigation system, and probably were planted at the same time when the house was rehabbed. The only difference is that the 2 plants on the end get an extra hour of direct sun. Can this extra sun be causing the yellowing leaves? Can anything be done to help bring these plants back looking like their cousins?
These plants like a sunny, sheltered spot, so the extra sunlight on its own isn't the cause - what might be, though, is that 2 hours extra sunlight means those plants and the soil they're in dry out more and require more water, so your irrigation, which is adequate for the others, may not be for these two.