The Seagulls led 1-0 after a sparkling first half-hour at home to London City Lionesses.
But an own goal and fine strike from Freya Godfrey - with City's only shot on target of the game - sent them to a 2-1 defeat.
It was a bitter disappointment for Albion after they failed to build on a 1-0 win at Everton last time out.
But they will look back at failings in front of goal, some bad luck and two big penalty shouts as they chased the game in the second half.
A beautifully crafted opener by Kiko Seike on 23 minutes was the least Albion deserved from an enterprising first half-hour.
The Japan winger curled home inside the far post after a layoff by Madison Haley.
Albion played some attractive, free-flowing and creative football but their momentum was punctured when Moeka Minami sent a cross into her own net under no real pressure on 36 minutes.
Seike and Nadine Noordam then both hit the post in separate attacks and the rebound of the second of those saw City counter to stunning effect.
Godfrey cut inside on to her left foot and curled a beauty into the far top corner just before the break
Seike had a glorious chance to level early in the second half but sidefooted into the side netting from close range after working her way into a great position.
Rosa Kafaji sent an effort across the face of goal.
And there were two penalty shouts for potential fouls on Madison Haley, of which the second – as Poppy Pattinson lunged in – looked the most convincing.
Albion continued to play under the interim management of Chris Roberts.
Head coach Dario Vidosic is in Australia, where his father Rado recently died after a battle with cancer.
Players and fans honoured Rado with a minute’s applause before kick-off.