The S&P 500 is near record highs. But some bearish technical headwinds may soon spell trouble for stocks.

According to John Kosar, director of research at Asbury Research, three charts show that a peak in stocks may already be underway:

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Kosar first looks at the Nasdaq 100 index. He notes that it failed to break above its September 2000 high of 4,147.19. While the Nasdaq 100 made a few attempts to rise above that level this month, it still has not done so and closed Wednesday at 4,073.57.

“Markets have a long-term memory,” he said. “Whenever you are bumping up against a big area like this, most of the time you’re not going to get through it the first time. …  Just looking at this chart all by itself, it suggests there’s going to be a problem just getting through here, at least first try.”

Kosar then looks at a chart of the assets in the ETF tracking the Nasdaq 100 (which trades under the ticker symbol QQQ). That chart just traded below its 21-day moving average, potentially spelling trouble for the overall index.

“When you’re looking to see if a market is going to break a level, the thing you’ve got to realize is the horsepower that gets it there is asset flows,” Kosar said. “And these asset flows are starting to pull in a little bit. In other words, people are doing exactly what you would expect them to do when you’re at a 14-year high—they’re taking some profits.”

For the full interview and accompanying video, click here.