The grammatical expression for this week is to “take a turn for the worse”, and it is used when we want to talk about a bad or neutral situation which suddenly becomes worse. For example:
My life wasn’t very good, but things took a turn for the worse when I lost my job.
My friend was in an accident. His condition was stable, but he’s just taken a turn for the worse. I’m so worried!
We thought the economy was getting better, but yesterday things took a turn for the worse when one of the biggest companies in the country declared bankruptcy.
Negotiations between the two companies took a turn for the worse yesterday when ABC Company demanded more money.
We can sometimes use this expression to talk about personal situations but, in my opinion, it’s more commonly used to talk about bigger situations like politics, negotiations and serious health problems.
It’s very common to use the word “things” in the sentence such as in examples one and three.