8.4V is not a current.
Are both cells same brand and same type?
The large difference may indicate that one is damaged.
To test: take a large 2 ohm resistor. Put it from plus to minus. Measure voltage over resistor. What do you see then? Voltage should drop a bit only...
Do not get burnt, the resistor will heat up quickly.
Also: do all this fast. The current will be large. This may damage your battery.