Rye and Iden United have not given up hope of winning the division one title after a 4-0 victory over basement side Shoreham took them into second spot.
An own goal, plus a brace by Micky O'Callaghan and a Peter Baker penalty gave Rye victory.
Rye manager Ryan Light said: "We shall keep fighting until the last ball is kicked."
Leaders Chichester dropped two points when Joe Leggatt levelled with two minutes remaining for Sidlesham after Paul Thomas converted a 53rd-minute penalty for the hosts.
John O'Hara League Cup winners Arundel capped a marvellous Easter by beating derby rivals East Preston 2-1 at Roundstone Rec with goals from Jason Wimbleton and Miles Scerri, who took his tally for the season to 47. Simon Clayton scored for East Preston.
Hailsham severely dented Eastbourne Town's hopes of the runners-up spot with a 2-1 win at the Saffrons as Nick Barden and Ashley Jarvis netted. Carl Harris replied for Town.
Pat Massaro grabbed a hat-trick as Three Bridges beat Horsham YMCA 3-0 - Bridges still have hopes of a top two finish.
East Grinstead were held to a 2-2 home draw by Redhill. Ben Burns and an own goal were on target for the Wasps, Luke Jones and Michael Morgan netted for the visitors.
At the bottom, Shoreham are relegated but Pagham beat Selsey 2-0, with Bryn Hauxwell grabbing a brace, to further strengthen their survival hopes.
Whitehawk beat Hassocks 2-0 with goals by Terry Cooper and Ryan McBride. Jon Donoghue (2) and Dominic Shepherd netted in Ringmer's 3-1 win at Sidley.
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