a) Your inputs (ECG, LF Noise, and HF Noise) do not have any reference. Typically the body is driven to a known voltage. It is common practice to use a right-leg drive circuit, as shown here: b) The INA333 and OPA333's are powered with 'VCC' and 'VGND' where VCC=5V...
AC Coupling with an integrating servo amp or an AC couple capacitor, Right Leg-Drive, Wilson Central Terminal, and several other circuit components. Below