Hi @trace60,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Is it possible to get some photos of your snow peas? It would be tough to diagnose and offer a remedy without seeing the issue.
Let me know if you need a hand uploading images, I am more than happy to help if required.
A possible reason is powdery mildew, which is a very common fungal disease, especially in warm, humid, or crowded growing conditions. It looks like a fine white or greyish coating on the leaves, stems, or pods, and can cause leaves to yellow, curl, and eventually die back if untreated. Does this sound like what you are dealing with?
If so, then start by improving airflow around the plants. Space them well, remove any lower or heavily affected leaves, and avoid watering the foliage (water at the base instead). You can then treat with Liquid Copper Fungicide. It is safe for use on edible plants, but you'll want to give them a good wash before consumption.
Let me know what you think.
Jacob
