Hi,
I guess the problem is mainly
* the power supply
* combined with the output_low_voltage behaviour (specification).
Your description misses some important informations:
* power supply voltages for all the Opamps
* how are the supplies connected
* power supply bypass capacitors
* what is the most right Opamp type? If also a dual (multi) Opamp, how is the remaining Opamp connected?
* PCB layout ... needed to verify if you followed the layout recommendations
* if you complain about "different voltages" the tell us the actual voltages. Otherwise it's meaningless for us. We don't know whether you talk about 1mV, 10mV, 100mV or 1V.
Klaus