I think the title is sufficiently clear.
To add a little more clarity, if a business is performing extremely well, we generally say it has "peaked".
Is there a word/phrase/idiom that implies something opposite to "peaking" in business context?
Usage Sentence: (Only tentative, answers can contain their own usage examples)
ABC Inc.'s Smart Phone business _______ when a recent survey showed that it sold only X(single digit) units and added less than Y (also single digit) customers in the previous quarter. It comes as a shocking surprise as the same company had sold 1 million units within the first week of its launch.
Nobody is buying ABC Inc's smartphones any more. Their business __________.