From Longman Dictionary of Contemporary Englishbe on the rocksbe on the rocksinformalFAIL a relationship or business that is on the rocks is having a lot of problems and is likely to fail soon SYN in trouble I’m afraid Tim’s marriage is on the rocks. → rock
Examples from the Corpus
be on the rocks• He was a good soldier, but his marriage was on the rocks.• There had been signs that their marriage was on the rocks for years.• His third marriage was on the rocks. 