The league leaders suffered a 2-1 home loss to Freiburg on Tuesday to crash out of the German Cup in the last eight, with the visitors grabbing the winner with a second-half stoppage time penalty.
Tuchel's arrival, following the surprise sacking of Julian Nagelsmann (35), was supposed to kickstart their season after a rocky start to the year saw their lead at the top evaporate.
He enjoyed a dream debut on the bench last week with a 4-2 victory over former club and title rivals Borussia Dortmund but was brought down to earth quickly with Tuesday's Cup exit.
"We are lacking the final pass, a bit of precision," Tuchel told a news conference. "We are lacking a bit of lightness, a bit of confidence and thus a bit of creativity."
"Overall we are lacking form. We should not make the mistake of analysing just tactics. We should become more resistant, develop some bite as a team," he said.
"We recognise we are not in top form but are on our way there."
With two titles left to play for and a Champions League quarter-final first leg at Manchester City on Tuesday, Tuchel has no time for major fixes.
"We need to show a reaction (on Saturday). We would need to show one even if we had won. We need to keep pushing, pushing, pushing because it is a tight race in the league and on Tuesday we have the next knockout match (against City)."
Against Freiburg, Tuchel will be without forward Eric Maxim Choupo-Moting (34), whose knee injury flared up again. The Cameroon international is also doubtful for the game against City, Tuchel said.
"It will be tight because he will not go to Freiburg today with us and then it will be tight (for the City game). We have to wait," he said.
Bayern, chasing an 11th straight league title, are two points clear of second-placed Dortmund at the top of the Bundesliga with eight matches remaining.
Follow their weekend clash against Freiburg with Flashscore.
