Folkestone Invicta suffered only their fourth Isthmian Premier defeat of the season on Saturday.
Jay Saunders’ men were beaten at in-form Billericay who scored the only goal of the game after 20 minutes through Elliot Long.
Invicta finished the game with 10 men after Liam Smith collected two yellow cards.
Chatham remain fourth after a goalless draw at Whitehawk but the four teams immediately below them all won – including Cray Wanderers and Dartford.
The Wands won 2-1 at home to Cheshunt thanks to goals from Max Fiddes and an Alex Hernandez penalty in the space of six first-half minutes.
Dequane Wilson-Braithwaite scored what proved a late consolation for the visitors.
On-loan QPR forward Rohan Ellis-Vaughan came off the bench to score his first goal for the club.
His 95th-minute goal was enough for the Darts to win 1-0 at rivals Welling United and leave the Wings six points adrift of safety ahead of a crunch clash against Cray Valley – who moved out of the drop zone at the weekend – on Tuesday.
The Millers won for the first time under new boss Kevin Lisbie, winning 1-0 at Lewes thanks to a third goal in as many games from Makise Evans.
The late kick-off at Southwood attracted a crowd of more than 2,000 as Ramsgate were held by high-flying Aveley in a 1-1 draw.
Solomon Ogunwomoju put the hosts ahead two minutes into the second half but Anthony Church equalised on the hour mark.
Sittingbourne tasted defeat for the first time under Reece Prestedge after going down 3-1 at AFC Croydon Athletic despite a first-half equaliser from Jean-Baptiste Fischer.
Faversham Town missed the chance to go above the Brickies after being held to a 2-2 draw at home to Herne Bay.
A crowd of 685 at Salters Lane saw Kamani Mcfarlane put Bay ahead but Tommie Fagg levelled immediately.
Frankie Smith put Faversham ahead in the second half but Rhys Wyborn levelled in stoppage time to deny the home side.
Rory Smith scored the only goal of the game as Deal moved to within five points of the top five after taking all three points at Sheppey United.
Crowborough played virtually all the second half with 10 men but left Margate with maximum points from a 3-1 victory. Player-boss Ben Greenhalgh had equalised for the Gate straight after the red card.
First-half goals from Gary Lockyer and Kai Garrett handed Ashford a 2-1 home win over Eastbourne Town at Homelands.
Erith Town lost 5-1 at leaders Three Bridges and VCD went down 3-1 to Broadbridge Heath but Beckenham extended their unbeaten run to five games with a 2-1 victory at fellow strugglers Hassocks.
