The pitch and speed of every project has now slowed down by 20 bpm and pitch has dropped for all instruments. I tried increasing the sample rate to see if that rectified the situation and it does not seem to change anything.
Also, I use a line 6 Helix as my interface. Upon starting up a project in cubase I received an error message stating the ports had not been mapped. I can post screen shots of this if anyone is interested and of my Bit depth/ Sample rate as well.
The thing that is throwing me off is that when I play the projects with no sound, just the metronome, the tempo is correct according to various reference metronomes. When I play with sound, all the audio matches the tempo but is quite obviously slowed down and the pitch has reduced slightly.
This is now the second time this has happened. The first time I simply reset my computer, 2018 iMac, and started up Cubase and all had been changed back to original state. I tried to do this again but that did not work.