disease or blight on cucumber plants
I'm a beginning gardener, and several of the plants in my first-year raised vegetable bed have turned awful in the last week or so. One tomato plant started the trend, starting several weeks ago--leaves and stems turning yellow and then brown and shriveled. But in the last week it hit the cucumbers (photo attached--I'm sorry it's sideways) and then the zucchini. I had aphids last week and sprayed a soap-water aphid-smothering solution on the plants every other morning a couple times. This current problem looks more like grey mold when I compare it to pics in the gardening books, but the conditions in my garden don't seem right for grey mold--the plants are widely spaced, and I'm in dry Southern California. The soil is a combo of organic compost and garden soil, and there are tomato fertilizer stakes in the soil around the tomato plants. I haven't otherwise fertilized the garden since we built it in early May.
I'm woefully inexperienced and in need of advice. What is ailing my plants, and what can I do? Thank you in advance for suggestions!