Answer: How disappointing for you to have a garden full of struggling plants! It does sound as though fungal infections are running rampant, and you may be playing host to a population of bud worms, as well. Bud worms can enter the unopened flower bud and feed to the extent that the flower is ruined and will not open. You can cut open a few of the dropped buds to see if bud worm damage is there. Bud worms are difficult to control because they are inside the flowers so you'll need to carefully inspect your plants on a daily basis, especially the unopened flower buds. If you see a small hole in the bud, a worm has entered. Your best defense is to pick the flower bud off the plant to keep the worm from feeding and turning into an adult. If you are diligent, you'll eventually reduce the population.
All plants need well draining soils, adequate sunshine, good air circulation all around and adequate water. When you provide these basics, they are normally healthy and happy. You might want to take the time to renovate your garden, digging the plants, amending the soil with organic matter, then replanting, spacing them far enough apart that they will have good air circulation all around. While it may seem like a huge undertaking, if you begin in one area of the garden and work your way around, your plants will be healthier and you won't need to spend time and money on insecticides and fungicides.
Fall is a good time to renovate a garden. Begin by digging the plants in your selected area and covering the roots with dampened newspapers to keep them from drying out while you're working. Then spread 4-5" of organic matter over the area and dig it in to a depth of about 8". Replant your plants and water them in well. They will probably wilt and look unhappy for a week or two until their roots become established again. When they perk up and show new growth you can prune away anything that looks dead or diseased. Eventually you'll have a healthier looking garden and your plants will continue to thrive as the weeks pass.
Best wishes with your garden!
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