Sunderland's unbeaten run is over after they lost at Colchester, while Leicester and Barnsley are virtually safe following crucial wins.
The Black Cats were hoping to extend their unbeaten run to 18 games at Colchester, but slipped to a 3-1 loss.
Dwight Yorke's header cancelled out Wayne Brown's opener for The U's, although it proved a false dawn.
Colchester never gave up and Richard Garcia put the home side in front before Jamie Cureton's (pictured) penalty settled the affair.
At the foot of the table Leicester are five points ahead of Leeds along with Barnsley, while Hull bagged a priceless point.
Nils-Eric Johansson's last-gasp strike secured all three points for The Foxes at promotion-chasing Preston.
A brace from Daniel Nardiello, his second coming from the penalty spot, lifted The Tykes over Crystal Palace.
Stoke missed out moving into the play-off spots after a late equaliser from Hull City at The Britannia Stadium
Liam Lawrence's goal looked like giving The Potters the points before ex-Leeds man Nick Barmby snatched a late point.
It proved a disappointing day for Leeds as they battled bravely with 10 men at Southampton before succumbing in the closing stages.
Bradley Wright-Phillips netted on 84 minutes to secure the win after Leeds had Alan Thompson sent-off in the first half.
Southend remain in deep trouble along with Leeds after losing 2-1 at Plymouth.
Peter Clarke cancelled out Sylvan Ebanks-Blake's early opener only for Barry Hayles to snatch a late winner for Plymouth.
QPR are safe as Dexter Blackstock's 23rd minute strike was enough to secure all three points against struggling Cardiff.
Sheffield Wednesday are two points behind sixth-placed Wolves after a 2-1 success over Coventry at Hillsborough.
Michael Mifsud levelled matters after Marcus Tudgay gave The Owls an early lead, but Brian Laws' side were not to be denied.
Steven MacLean struck with 20 minutes remaining as Wednesday bagged their fifth successive win.
Click below for match summaries:
Barnsley 2-0 Crystal Palace
Colchester 3-1 Sunderland
Plymouth 2-1 Southend
Preston 0-1 Leicester
QPR 1-0 Cardiff
Sheffield Wednesday 2-1 Coventry
Southampton 1-0 Leeds
Stoke 1-1 Hull