I think the correct output of Va should as the output but of opposite phase, If ur circuit is fully differential. The pmos transistor connected to ur output is diode connected. try to simulate the circuit with its gate terminal connected to the other pmos gate & observe the output.
Check that ur circuit is fully differential.
For sure that you made a mistake when you typed in your netlist. Check out that transistors sopposed to be equal are equal. Verify that transistors are connected to what they should.