"passed the peak" is correct and usable in written English.
You can use it to describe something that has reached a maximum level and that level is going down. For example, "Sales of the new video game have passed the peak, and now they have started to decline."
Besides, the Lib Dems have already passed the peak of their power.
The marches may have "passed the peak", adds Dieter Rucht at the Berlin Social Science Centre.
The company has passed the peak of its patent expiry problems and the shares remains a solid yield play.
When Thoreau left Walden, he passed the peak of his career, and his life lost much of its illumination.
Like many other experts, he argues that we have passed the peak of oil production, and it's all downhill from now on.
I terminate the first pass after either searching to the upper limit of my range (250mm) or after I've encountered 10 monotonically decreasing values, hence indicating that I've already passed the peak.
But it is now shooting upward at the high trajectory angle of a North Korean rocket, has passed the peaks of the last two seasons and is on track to match or surpass 2014-2015.
He then presents evidence that we have passed the peaks for water, fertilizer and land, and that we will all soon be made painfully aware that we have passed it for food, as wealthy nations experience shortages and rising prices, and poorer ones starve.
A tower representing 100 million business cards runs up one side, passing the peak of Mount Everest about a third of the way up the image.
Amy, at 40, is at the peak of her skills (if perilously close to passing the peak of anything more intimate) and she recounts her triumphs with infectious shrewdness and glee.
While the tornado was passing, the peak gust wind velocities were estimated to be from 52 m/s (187 km/h) to 72 m/s (259 km/h) in the studied area.
