I live in the Phoenix, Arizona area and have a tomato plant in a clay pot. Over the past several weeks, not only are the leaves turning yellow, but the whole plant appears to be becoming yellow. There are no new leaves forming, no buds, the plant just seems to be shutting down. There are several tomatoes on the vines which are not growing or turning red. I water every day as the whole plant seems to wilt if I skip a day. The soil is always moist. Questions: What is causing the yellowing, and is there anything I can do to reverse the process and save my plant?
This could be due to a nutrient issue, pests or disease.
This link will help you pinpoint the cause.