Footage keeps changing color

Hello guys, Mario here, I'm working on my footage and i keep having the same annoying problem, my gopro footage keeps changing colour mid footage from slightly lighter to slightly darker. I thought at first it was just final cut doing its thing and would be corrected when i export the project but i recently created a master file and the same thing keeps happening! I have a late 2011 macbook granted, but before i upgraded from 10.0 to 10.3 i didnt have this problem! The colour change also causes frame drops, im not using any color correction or anything just cutting and adding clips to the timeline in their original form. If anyone could help me i would really appreciate it.