Playback latency on only one track stack?

Another very strange issue that probably no one can help with...

My project, again, has become rather large, and last mixing session I was experiencing what I thought was just latency (my mac had been on a significant while, the project was getting large, etc.) so I saved and quit Logic and may have turned my mac off then or a little while thereafter.

So I've come back to the project today and it appears that there is no latency except for on one track stack. I have three layers of my bass in a track stack and somehow they seem to be exactly 1/8 late. They play at the exact same time as the piano which is 1/8 earlier than it.

I don't understand how this is happening when I haven't touched anything that could change such things.

Pleaaaase can someone give me a hand because this is for uni coursework, due very soon