Answer: From your description, it sounds like Botrytis, a fungus also known as gray mold. It shows up as brown spots that may turn black, and finally gray. It thrives in warm, humid conditions. To minimize problems, space bulbs properly to avoid overcrowding plants and to improve air circulation, water early in the day so foliage will dry before nightfall, and don't get the foliage wet. In other words, water the soil, not the plants, and don't let soil splash up on the foliage. Remove any infected leaves and destroy all dead foliage, and discard diseased bulbs. There are some new soap-based fungicides that are kinder to the environment than many other commercially available fungicides, and can be effective on gray mold.
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