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Shige Honjo, a veteran hardware chief at Nest, and Scott Mullins, a senior engineering manager, are leaving the company, according to multiple sources.

Honjo, the director of hardware design and engineering, will depart at the end of May. Mullins is shifting over to Google to work on the next iteration of its Glass wearable, dubbed Project Aura internally. (He’ll continue to work for Nest CEO Tony Fadell, who runs Aura independently of Nest.)

Both Honjo and Mullins reported to Nest’s number two exec, VP Matt Rogers. While they are key leaders at the company, the pair are not on the senior team that reports into Fadell.

Still their exit comes amid a steady stream of departures from the connected-device unit under Google parent Alphabet, as pressure mounts on Nest to improve its sales targets and right its increasingly rancorous culture.

A Nest representative declined to comment.

Honjo, in particular, is a big loss for Nest. He was the second employee ever, coming over from Apple in 2010 along with the company’s founders, Fadell and Rogers.

In 2013, the year before Nest was acquired by Google, Honjo was promoted to Nest’s executive team. Former Nest employees describe Honjo as a critical troubleshooter internally; one called him the “firefighter” for Fadell and Rogers. Honjo’s wife and brother both work for Nest.

Mullins, who joined Nest in 2012 as director of hardware engineering, also came from Apple, where he worked on the iPhone hardware design.

As we reported earlier this week, Nest’s overall sales — around $340 million in 2015 — have lagged behind the initial expectations that Google set with the purchase two years ago. Nest’s operating budget from Google as well as the vesting schedule for its top executives are likely to sunset this year.

The imminent departure of Honjo and Mullins places more pressure on Rogers, who manages most of the day-to-day affairs at the company.

Update: A previous version of this story listed Honjo as VP for Nest. A Nest spokesperson confirmed that he held that title and was on the executive team prior to the Google acquisition, but that changed following it.