So I'm starting to build outer planetary bases in KSP with a relatively decent computer. I find it weird because I've built lots of stations in orbit in the past and they've presented no problem to my computer with an average fps of around 30+ and these can be stations with over 200 parts. However, when I started landing modules of bases on other planets, once they've exceeded 50 parts, my computer experience extreme unplayable lag that can reach 3 to 4 fps which I find unreasonable given my PC specs and me launching rockets with over 100 parts with no issue. For example, this Europa base of mine can only be played at 4 fps when I'm within 300 meters to all of the modules.
My PC specs are: Windows 10 Pro 64-bit, Intel Core i7 4790, 16.0GB Dual-Channel DDR3 & GTX 970. If anyone has had similar issues in the past and found a fix for the issue or even the cause of it would be really great, thanks.