Following quarterly reports which spooked investors over the state of digital ad spending, Pinterest Inc. and Snap Inc’s stocks fell about 18% each on Friday.

Their quarterly reports released late on Thursday were a surprise, coming after much stronger showings in the reports from two digital advertising heavyweights, Alphabet Inc, and Meta Platforms. Their strong showings are being taken as evidence that as the economy cools, advertisers are shifting away from smaller platforms, and focusing on the bigger players in the new uncertain economy.

Pinterest warned on Thursday that its market remained uncertain going forward, after reporting second quarter revenue growth below analyst estimates. The image-sharing app is grappling with a pullback by advertisers as the economy slows.

Snapchat parent company Snap also missed Wall Street estimates for revenue, which it attributed to changes to its advertising platform which hurt the demand for its ads. Its report warned that the company may see next quarter’s results also fail to meet Wall Street estimates.

Snap also noted it had taken measures to increase the relevance of ads shown to users, and due to that some advertisers were seeing fewer “actions,” such as ad-clicks.

On Friday, Monness Crespi Hardt analyst Brian White wrote in a client note, “Aside from Snap’s internal issues, the competitive landscape remains daunting, and we believe the darkest days of this downturn are ahead of us.”

The sell off cost the companies a combined $6 billion on value, as Pinterest’s valuation fell to $15 billion, and Snap saw its value cut to $13 billion.

12 analysts cut their price targets for Snap, as seven cut their price targets for Pinterest.

Since Wednesday, shares of Meta Platforms surged 13%, due to Wednesday’s report from the Facebook and Instagram parent, which issued forecasts for quarterly revenue which were well above the expectations of analysts.