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Drawing hard on a battery - such as pulling hundreds of amps from it to start your car - is generally a quick way to get your cells out of balance. However near identical each is, there will be tiny differences in internal resistance, and, more likely, in the wiring between each cell.
Of course, if the caps are doing the starting, and you’re drawing reasonable currents, that’s a moot point.
Since there are only 4 in series, it wouldn’t be hard to put some zener diodes and a resistor across each string so that it would bleed them all down to the same voltage and keep them balanced. Then again, a simple, cheap bms could be set up strictly for charging (bypassed for heavy draws) and save you oh the bother.
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