1. From your waveform, I see that ur v(4) is too high to make the CMFB PMOS in active region. because if your common mode voltage is 2.5V , then the Vdssat of top CMFB PMOS is (5-2.5-|Vtp|)~=1.5V, but the waveform show that u only have 0.2V around, so ur CMFB loop gain is such small that it can't not set the correct CMFB voltage.
2. From ur waveform, ur common voltage is not 2.5V. it is above that. the formulat for common voltage is Vcom=(Vout+Vout1)/2. u can use awave to calculate that value.