Answer: The Knockout roses are considered extemely disease resistant, including black spot, so I am not certain what you are seeing on the foliage there. You might try removing the worst affected foliage and any fallen foliage, avoid wetting the leaves when you water and contact your local Cornell county extension for assistance in identifying the problem. Once you know that, you can decide how to treat for it.
The symptoms on the burning bushes might be related to lack of soil moisture, or to overfertilizing, or to accidental chemical/herbicide exposure. Again I would suggest you consult with the county extension for a more specific diagnosis. Based on knowing that, you can determine how to proceed. If a chemical control is needed, they will have the most up to date information on what to use and how/when to use it for maximum results.
For both the roses and the burning bushes it may be helpful to provide a photo of the overall plant and area where it is growing, as well as a freshly collected leaf sample or two showing representative damage and enclosed in a clear plastic bag and kept cool so it stays fresh.
The little maple wilting seemingly overnight could have been due to verticillium, however when the entire tree goes all at once -- rather than progressing a few branches at a time -- I would tend to suspect extreme root damage such as by a vole, or accidental herbicide exposure, or reaction to a spray of some kind.
I'm sorry I can't be more specific for you but I hope this helps you begin to trouble shoot.
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