Ignition coil pack gives less spark

One terminal of ignition coil pack gives less spark than its adjacent terminal of the same coil pack. The same is true for the other coil pack. All resistances relating to primary and secondary circuits in each of the 2 coil packs are all within specs and have equal readings in each circuit respectively.

Now, my issue is why less spark is produced from one terminal afterall the coil packs are of well within specs readings. Also, it's rpm drops from 850 to 630. It's i20 1.2 petrol car.

Thanks.