But now, Matt Maley of Miller Tabak says their rallies are showing signs of fatigue.
"I'd be a little cautious on all these names right now. Just on a purely technical basis, they're getting quite overbought," Maley told CNBC's "Trading Nation" on Thursday. "Last week we saw a big correction or pullback in the stock market that worked off the overbought condition. It didn't work off the overbought condition for any of these names and they're getting more overbought."
Their weekly relative strength indexes of momentum are signaling that the rally may have become overheated. Zoom, for example, is trading at above 80 on its RSI. Any reading above 70 signals overbought conditions.
"The one that's the most overbought is DocuSign which is approaching 90 now," said Maley.
"I'm not saying that people shouldn't continue to nibble at them here. I just think that they are getting ripe for a little bit of a pullback, and so people should be a little bit less aggressive up at these levels and look to buy them if they do see any kind of a 5% to 10% pullback with the rest of the market," said Maley.
The SKYY cloud computing ETF is up 22% for the year. Zoom is its best performer, up 255% this year.
John Petrides, portfolio manager at Tocqueville Asset Management, says recent trends and strong fundamentals should propel these stocks over the long term.
"They're light on capex, which means they generate a lot of free cash flow. And by and large, most of these companies do not have a lot of debt on their balance sheet. They have more cash than debt," Petrides said during the same segment. "They generate a lot of free cash and a healthy balance sheet, and they're in thematic investment plays such as work from home, that has a long runway to go."