It looks a bit like mite damage - that stippling/spotting of the foliage is pretty characteristic of their damage. But I see no sign of mite damage on the flowers and they seldom infest flowers anyway.

The Bayer product is not all that effective against mites. It's active ingredient, Imidacloprid, has very poor results with their control. I'd try Neem oil instead, covering both surfaces of the leaves and the stem carefully. Also, I'd spray the plants down frequently with water. Mites like warm and dry conditions and creating a more moist/humid environment around the plants will discourage them. As long as you do it early enough in the day for the foliage to dry before nightfall, there is minimal disease risk. Powdery mildew is actually unable to thrive and develop on wet surfaces and the Neem is also a good organic fungicide that will discourage any other fungal issues.

I have used neem oil and insecticidal soap before but I am trying to release beneficial insects to see how that works. No difference so far. Mites make the rounds here starting in May-June, although this year they were late due to all the rains. They like to nibble the edges, which then brown out and that gives leaves the brown look on the edges + the stippled look on the rest of the leaf. You need to look for them using a magnifying glass. You can also get a 8.5x11" piece of white paper, put it under the shrub and shake the leaves to see what falls. If dots fall on the paper and the dots move, those are mites. They also produce a lot of webbing which should be visible by this time of the year. New leaf growth probably hates the webbing. They do not appear interested in the sepals at my place but, it is time for the hydrangea sepals to begin changing their shade of color or even the color depending on which hydrangea one has.

I doubt you will loose the leaves if you use neem oil or insecticidal soap per label directions. You may "naturally" loose leaves when the plants go dormant in Nov or December though. You will get new replacements for the damaged ones in Spring 2016. But should you loose one 'due to the mites', it is up to the plant to decide whether to replace it or not. It may leaves now or wait until Spring 2016. The plants should return in good shape if you take action now. Mites like hot and dry so now is their time.

Mites do not "nibble" or chew. They are sucking insects only and live on the juices (sap) they suck out of plant tissue - that's why they tend to leave flowers alone. Any chewed or nibbled edges are due to some other insect pest. Also, not all mire issues are due to spider mites - there are many other species of mites that produce no webbing.

Thank you all for the information. I will neem oil and treat them all this weekend.