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Hi Rosey, There are a number

Hi Rosey, There are a number of things that could be causing this. It could be a plant disease, such as Powdery Mildew or Mosaic Virus. You can see pictures and tips here: http://www.almanac.com/topics/gardening/pests-and-problems Or, it could be something as simple as overwatering. Try easing up on the water, and give plants a dose of nitrogen rich fertilizer. They need good drainage and full sunlight. Crop rotation from year to year is also beneficial.