It was most probably conflicting with libsass or something else from Foundation side.
I solved it by adding options and setting "sortDeclarations", "consolidateViaSelectors", "consolidateMediaQueries" to false.
cssc: {
build: {
options: {
sortSelectors: true,
lineBreaks: true,
sortDeclarations:true,
consolidateViaDeclarations:false,
consolidateViaSelectors:false,
consolidateMediaQueries:false,
},
files: {
'css/app.css': 'css/app.css'
}
}
},