Cardiff pulled 10 points clear at the top of the table, while Alex McLeish endured an afternoon to forget on his return to Birmingham.
Elsewhere, Hull City closed back in on the automatic promotion places, Crystal Palace tasted derby success, Middlesbrough came unstuck again and Peterborough remain rooted to the foot of the table.
Cardiff took another positive step towards the Premier League on Saturday, with a solitary effort from Fraizer Campbell enough to see them edge out Leeds at Elland Road.
Hull City are now level on points with second-placed Leicester following a 1-0 victory over Millwall, with David Meyler's first-minute effort settling the tie.
Watford are also in the hunt for a top-two finish, with Gianfranco Zola's side recovering well from falling behind to a penalty from Hornets old boy Marvin Sordell to claim a 2-1 win over Bolton.
Middlesbrough's promotion push has come off the rails in dramatic fashion, with a 4-0 defeat to lowly Ipswich seeing Tony Mowbray's men suffer a fourth straight setback.
Brighton missed the chance to close the gap on Boro as they went down 3-1 at Sheffield Wednesday, with Ashley Barnes seeing red at Hillsborough.
Crystal Palace remain inside the top six and picked up their first win in four as Glenn Murray netted twice in the space of four second-half minutes to secure derby spoils for the Eagles in a clash with capital rivals Charlton.
Alex McLeish took Nottingham Forest to his former employers Birmingham, but saw Chris Burke - a man he tried to sign during the January transfer window - net twice at St Andrew's to send him home empty-handed.
A deadly double from Jordan Rhodes saw Blackburn deny Bristol City a third win on the bounce, with Rovers prevailing 2-0 at Ewood Park.
Derby secured just their second win in seven outings as they found their scoring boots in a home date with Huddersfield, with Craig Bryson, Jamie Ward and Richard Keogh on target in a 3-0 success.
Barnsley offered their survival bid another welcome shot in the arm, with Jason Scotland stepping off the bench to grab an 88th-minute winner for the Tykes as they overcame 10-man Blackpool 2-1.
Finally, Peterborough came within five minutes of moving off the bottom, but saw Martin Paterson snatch a late equaliser for Burnley in a 2-2 draw.