Premiere Pro is playing project in slower speed

Hi,

I opened my almost finished project and for some reason the playback speed has slowed down. 1 second in the program is not anymore 1 second. This is not a ram or memory related issue. Every project that I open now plays "slower". Speed in every individual clip is set to 100% and the frame rate also matches the same 25 that I used to film. What have I done and how do I fix that my 25 fps project plays 25 frames in 1 second?