Hi Fisher,
You don't say what type of plant spray you used, but what in the world are you spraying for when you don't know what is wrong? Know thine enemy! If your plant is stressed, then you could make it worse.
Do you know which hydrangea you have? Could it have purple color to the leaves because the variety you have is supposed to have purple leaves? Is it in too much sun? Take a look at this site before you do anything else. Once you id your hydrangea, you will be able to find the proper growing requirements and might be able to diagnose the problem, which I suspect could just be stress from lack of proper watering, or you have an oakleaf hydrangea whose leaves turn a dark burgandy late in the season. Newly planted hydrangeas need lots of water.
Pruning should be done at the proper time of the year depending on which type of hydrangea you have.
http://www.hydrangeashydrangeas.com/index.html
Newt