Different results with different simulators

I'm doing a post-layout simulation, and set the DUT (it's called offset_gen_layout in this case) as Calibre view. Then I opened ADE L and started the transient simulation using ams by default (as I used an ams template when creating the config view). If I changed the simulator to spectre, the simulator gives me another result. Why is this happening? Shouldn't I be using ams? Are the transistor models different in these two cases?

EDIT: There's a notice saying:'GminDC = 1 pS is large enough to noticeably affect the DC solution.
dV(I3.VTEST1_515) = -1.79634 mV
Use the `gmin_check' option to eliminate or expand this report.
Bad pivoting is found during DC analysis. Option dc_pivot_check=yes is recommended for possible improvement of convergence.'

I then changed gmin to 0.1pS, and the result is almost the same.