Water irrigation system - control three valves from one pin, how?

Those may work, not sure of the dimensions.

I have used the ones I linked.
You can easily adjust the pressure either by lowering the voltage or adding a Y connector tube.
One leg of the Y tube has an adjustable clamp to regulate that legs flow.
The other leg just returns it’s water to the same reservoir the submersible pump sits in.
You can also feed the pump output into a trough that acts like manifold the length of the area to be watered thus reducing water pressure.

I’d stay away from valves and just use several inexpense simple pumps.