What part of the country are you in, Wnickell? Have there been changes in the local environment this year, such as digging around the roots, or the removal of a shade tree? Are they on the property line, and is it possible that your neighbor did something with digging or weed killer? Has there been a change of soil grade in the past few years?
When I see wilting or brown leaves on a plant in moist soil, the first thing that I think of is root damage.