Hoffenheim stumbled to a 2-1 defeat at Wolfsburg on Sunday as all six clubs chasing Bayern lost over the weekend.
Bundesliga leaders Bayern Munich saw their winning run come to an end as Schalke battled to a 1-1 draw at the Allianz Arena.
Neven Subotic has joined Cologne on loan from Borussia Dortmund until the end of the season.
Hoffenheim suffered their first Bundesliga defeat of the season as they went down 2-1 at RB Leipzig.
Hakan Calhanoglu scored twice as Bayer Leverkusen beat Hertha Berlin 3-1 on Sunday to move up to eighth in the Bundesliga.
Bayern Munich moved above Leipzig at the top of the Bundesliga, 11 days before the top two are due to meet at the Allianz Arena.