Question
The leaves on a one of my mature hydrangaes suddenly started getting brown and curling up.  20 feet away another smaller bush is starting to show signs.  Is this a fungus or a bug?

Answer
If there is a purple margin around the brown area, it would be a fungus.  If no purple is there, I would say it may be getting too much water.  If this is the case, cut back on the water a little.  You can remove the brown leaves and destroy them.  Keep me posted as to the condition of the plant, as they can go downhill fast if it is a fungal disease.  Good luck. Thanks.