George Barker scored twice and missed a penalty as Albion's under-18s lost a seven goal thriller at Gillingham.
Barker saw his second half spot-kick saved well by Gills keeper Conor Quinn, before the home side stunned the Seagulls with a quick-fire double to secure the victory.
And now new youth team boss Steve Brown - who will work alongside Centre of Excellence manager Vic Bragg - says the Seagulls must work hard to eradicate defensive errors.
He told seagulls.co.uk, "We scored three away from home, which normally you would expect to get a least a draw from, but unfortunately we conceded four poor goals.
"In the first two games we haven't played well defensively. Myself and Vic have worked hard on that during the two weeks that I've been here, and we're slowly getting our message across.
"At the moment mistakes are being made, but we will iron that out.
"We play some good football. Brighton are well known for playing good football, and we're still doing that, but we just have to stop the avalanche of goals we're conceding."
Gillingham opened the scoring after 26 minutes when Tom Murphy's shot beat Josh James in the Albion goal.
But the Seagulls equalised seven minutes later when James Smith capped a well-worked opening with a powerful shot into the opposite corner.
Smith and Leon Redwood had chances to put Albion in front but it was Gillingham who found the net again in the 55th minute when Callum Day slotted the ball past James.
Albion were soon on level terms again, for two minutes later Barker outpaced his marker before hitting a low shot into the bottom corner.
The Seagulls were then awarded a penalty when Ide was pulled down in the area, but Quinn guessed the right way and beat away Barker's spot-kick.
Having survived the penalty scare, Day and Murphy both doubled their tallies in the space of six minutes to give the Gills a 4-2 lead.
Barker pulled one back with a stunning shot into the top corner, but it was too little too late for the Seagulls.
Albion: (4-4-2) James; Strong, Sheriff, Dunk, Bolwell; Redwood, Hayward (Caskey 57), Ide, Smith; Barker, Hider (Cumming-Bart 70). Sub not used: Cooper.
