Deb Callahan seen in performance at WXPN’s All About The Music Fest in Camden, NJ in 2011. KENNETT SQUARE — For its second weekend of  “Act II”  of The Flash, the venerable downtown venue will host the blues and soul stylings of Philadlephia’s Deb Callahan – one of the region’s top vocalists for more than a decade. Although Callahan grew up in the Boston area, she...