FPS degradation every time I play in viewport

Okay so I’m a little stumped on this, and maybe I’m posting this in the incorrect forum, but I’m not too sure where else to post it. I’ve got a rather complex scene, with a rather complex level blueprint, and every time I start up the editor and play in the viewport, I get 120+ fps and <=8ms latency. The second I hit play I’m instantly at ~80 fps and ~12ms latency, no changes to the scene whatsoever. After that the fps slowly decreases every time I hit play. I’m not very versed in programming (only about a year of C++), but it seems like some kind of cache is being filled up and I don’t know how to go about debugging to find out what it may be. If someone could lead me in the right direction in terms of debugging, or if you have any idea what could be causing this problem, that would be fantastic. Thanks!