Two key components of Elon Musk's empire are under pressure, and some analysts don't see relief in sight anytime soon.

Shares of SolarCity and Tesla Motors, both co-founded by Musk, have taken hits recently. Tesla, once a darling of Wall Street, is down more than 16 percent in the past month alone despite a warm reception for its Model 3. Meanwhile, SolarCity was walloped this week after quarterly earnings fell short of market estimates.

UBS auto analyst Colin Langan, who has a "sell" rating on the Tesla, thinks the luxury automaker will be facing some stiff competition in the next few years from Mercedes, Porsche and Audi. BMW is also pushing to get a luxury electric sedan on the road by 2021.

For those reasons, Langan believes Tesla is overvalued. He also takes issue with the company's aggressive production target of 500,000 cars by the end of 2018. Tesla own estimates for production were bullish. It cited demand for the Model 3, its mass-market car expected to hit in 2017.

"That's a very aggressive target, even for any established automaker, so I think that's very tough to achieve and that's going to put the stock at risk," he said in a recent interview with CNBC's "Power Lunch."

"And there's a question of can they actually continue to grow, given they already have actually pretty good share in the high-end luxury sedan segment."