Hello - What is the goal of this circuit?
Your schematic is confusing if not completely wrong.
The left side of the Wheatstone bridge seems connected to both VDD/VSS supplies of your amp. The R6 gain resistor seems like it should go to VSS too.
It is not clear what loop you are simulating for the Bode plot.
However, the gain starts off -12dB, so it seems like a wrong test.
The phase does not quite move 180deg, but if you are in the wrong loop, it is meaningless.