LEDs do not pull voltage, they pull only current. Those drivers you have are constant current drivers and they increase the output voltage until the set current flows. The fact that they are having to provide more voltage than you expect can mean one of two things.
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The impedance of the LEDs is higher than you expect. This could be due to faulty LEDs, or a bad joint in the wiring, not a short. Or higher than expected forward voltage on the LEDs, you could try removing a couple of LEDs from those two chains and seeing if things change.
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Something interfering with the current measuring part of the circuit like interference or cross talk between the other circuits and drivers.