After a drop in big technology stocks Friday caused the Nasdaq composite to post its worst week of the year, the shares came under pressure again on Monday after Apple shares were downgraded.

Mizuho Securities' Abhey Lamba downgraded the iPhone maker to neutral from buy on Sunday, saying the best-case scenario is priced into the shares. The analyst echoed a common concern by investors taking profits in big technology stocks last week.

"The stock has meaningfully outperformed on a YTD basis and we believe enthusiasm around the upcoming product cycle is fully captured at current levels, with limited upside to estimates from here on out," wrote Lamba, who cut his 12-month price target to $150, which is about one dollar above where Apple closed Friday.

The Nasdaq 100 index dropped more than 1 percent. Shares of Apple were off by more than 3 percent in early trading Monday. Alphabet, Microsoft, Facebook and Amazon all fell by more than 2 percent.

A Friday sell-off pushed the down more than 1.5 percent last week, but the selling was worse among the biggest stocks. Apple, Alphabet, Microsoft, Facebook and Amazon lost nearly $100 billion in market value on Friday on no specific headlines, but rather investors questioning whether valuations for the names were getting ahead of themselves.

"At 15x and 11x NTM EPS and FCF, the stock is trading near the upper-end of its recent valuation range and we believe it is tough to expect the multiple to expand," wrote Lamba of Apple. "With limited upside to EPS or FCF estimates, we think the stock is fully valued."

Apple, Facebook and Amazon are still up more than 27 percent so far in 2017. Alphabet is up 20 percent and Microsoft shares are 11 percent higher for the year. By comparison, the S&P 500 is up more than 7 percent year to date.

"Our most bullish case yields earnings of about $11 for FY18, which is only $0.50 above consensus," the Mizuho note said on Apple.

This is the second week in a row a Wall Street analyst has bailed on Apple on a Sunday evening. Pacific Crest downgraded the stock to start last week to sector weight. There are now six analysts with hold ratings on Apple and 25 who rate it a buy, according to TipRanks.com. Despite the valuation concerns, zero Wall Street analysts have a sell rating on the shares.

— With reporting by CNBC's Michael Bloom.