Wrecks outside LoS lowers FPS more than wrecks inside LoS

I self-destructed some 1500 Swifts.

When the wrecks are in view but outside LoS I get like 20 FPS.
When the wrecks are in view but inside LoS I get 40-50 FPS.
Is there a setting I can change to increase the FPS here?