Some definite amount of ohmic resistance ought to be ahead of your filter. Looking closely, that appears to be a resistor just above the waveform generator at left. Is that your intention? Does the simulator understand that is 50 ohms input resistance?
Another thing to try is to put a low-ohm resistor inline with inductors (and perhaps also capacitors ). You have LC loops which lack any resistance. It's able to resonate (or ring) endlessly, once it's instigated. With ideal components, the simulator believes it has unrealistically high Q. The result is unrealistic frequency response.