Answer: Rather than improper soil pH, I would suspect a soil-borne disease of some sort. (Although it never hurts to run some basic soil tests to check nutrient levels and pH.) Some disease spores can live in the soil for years, so it's wise to avoid planting the same type of plant in one location year after year. You might try adding copious amounts of organic matter to the soil to try to help it recover and establish a healthier microbe population that can help keep disease organisms in check.
Q&A Library Searching Tips