From discharged, charge the pack. Monitor the temp. The warmest one will likely be the dead cell.
Otherwise, check individual voltage when fully charged. the lowest voltage should be the culprit. Also, if the cell matched the one that heated up differently, you have even better evidence.
The newer side by side dischargers ie dpd or ctx-d will give this info but pretty expensive way to go unlless you want to be fairly regularly pulling cells apart for optimization.
I am not an expert by any means but, I think this will get you started.