Automatic hydroponic brain

Hi, I'm currently working on a "brain" for my hydroponic growing tower(it's a vertical tower that pumps water from the reservoir on the bottom, up to the top and it drips down).

The idea is to have a pH sensors, TDS (ec sensor that measures water quality and thereby nutrient amount), temperature sensor, 12v water pump, 16-channel relay board, 12 pcs peristaltic pump (controlled via the relay board) and a ultrasonic distance sensor.
I'm using an arduino mega for this.
What i'm aiming for is for the pH and TDS sensor to automatically add pH +/- and nutrients from a specified profile in the code.

Now, the problem im having is that the pH-sensor and TDS sensor are both using voltage difference in their probes to determine values and when both probes are in the same water, they interfere with each other. It have tried to isolate the circuits so that when A is high B is low, it did not work. I've also tried to use a oscillator circuit that activated pH sensor and deactivated TDS and vice-versa. It also did not work.

I'm stuck, any thought on how i should proceed?
Thanks in advance
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i'm curious to see the datasheets for the two probes

Perhaps you can put one of the sensors in a water filled well by itself and arrange that water trickles in and out.

Or figure out a way to have the Arduino de-power each of them in turn.

Post the part numbers for the probes and your code. I'm certain there is a solution.