Your current source can generate any voltage in the range of the output of your opamps, so it can swing out of the range of the multiplexers and Arduino and force current through their protection diodes. Bad news, don't do that.
Current sources will use whatever voltage possible to push the programmed current out (here limited by the output swing of the opamps and their supply voltages). You have to ensure that either the voltage compliance of the source is limited to the 0..5V range, or that you have Schottky clamps to divert the current away from the logic chips protection diodes. Its possible to send CMOS chips into a latch-up state if you force current through the protection diodes - google "CMOS latch-up"