To add a further clarification, if the PCB had tripped, the cell would also be reading 0V. However, given that these cells basically look like they burned up, the PCB did not trip properly on those. The PCB should have tripped before the batteries got to this state. I noticed that 2 batteries look like they are in better condition. Are those the 2 that read 0V? If so, then my guess is that protection tripped properly on those 2 but not the other 2.
TBH, I always thought these Olight batteries looked questionable and this does confirm that it was at least part of the problem.
OP - You mentioned that you like buying different colored batteries to segregate mated sets for each light. Instead of doing this, I would recommend finding good cells at one location and you can just label them with a sharpie. That's the easiest way I've found to ID batteries and keep them together.