four o clock disease

[Paul Urzi]

I have been growing four o clocks for many years with no problems. This year they started out great, but now have a serious problem. The leaves are turning yellow and falling off from the bottom of the plant continuing to drop until the entire plant is bare. I have cared for them this years as in the past, with the same fertilizer and watering schedule. I am at a loss as to what to do.