Waterlevel sensor disrupts PH reading
That water level sensor uses bare metal which is in contact with the water. The PH sensors are sensitive for that kind of voltage in the water, even if it would be 0V.

There are isolated PH sensor amplifier modules. On forums are often discussions whether to ground an aquarium or not for a PH sensor. With a isolated PH sensor, you avoid most of those problems.

There are also non-contact water level sensors. For example capacitive sensor or even sensors that can be attached on the outside. Some sensors use the water pressure, but I don't know if this one is isolated: https://www.sparkfun.com/products/10221