Purchased and planted a Miss Kim Lilac in Longmont in June (?) Planted on a sunny slope with other lilac, shrubs, flowers in a rich soil blend with humus, topsoil, peat, etc Watered regularly throughout the Summer with well water, at least two or three times a week. Fertilized, mycorrhizae, worm "juice" A dwarf and a boomerang are doing well but Miss Kim is suffering. No signs of powdery mildew or leaf borer that I can see Leaves are curling and turning brown in spite of extra watering Any comments, thoughts, suggestions are gratefully appreciated

It's hard to make a definitive diagnosis based on just pictures, but we're wondering if perhaps it's getting too much water for what it can handle.  Before watering, feel around the soil and skip watering until it doesn't feel moist. 

The symptoms look like leaf scorch or sun scald

https://extension.colostate.edu/topic-areas/yard-garden/leaf-scorch-2-911/

As that says, it is important to water infrequently, but deeply.

If indeed this was planted in June, it soon got very hot, likely before the plant had a chance to settle in and extend its root system.  It's not clear to us from your text if your other plants were planted this year or previously.   If it is leaf scorch, there's not much to do now except wait until next year, hoping that it will be healthy enough to establish a better root system by the time the summer's heat arrives.  Earlier, besides not overwatering, one could use shade cloth, but now, the sun is very much less intense than it was in the height of the summer, and rapidly continuing to diminish, so the shade cloth is not going to be of much help.

The pictures also look like a fungal disease found on the East coast, but we could find no references to it having occurred in Colorado.  If you want to check out other options besides leaf scorch, you can, for a fee, take a plant sample to the Jefferson County extension, which is doing in-person diagnosis this year.  Here's details about that

https://jeffco.extension.colostate.edu/horticulture/clinic/