FPS drops are not my thing per say, as I'm not a gamer but here is my stock standard response, see if anything helps.
if you have your PC as lean and clean as you can make it, that's part of the battle.
sadly, the other parts may be outside your control like; number of users of your network, bandwidth, line attenuation, signal to noise ratio, etc.
logging into your modem's config menu will show these values.
but things you can control are;
• reboot modem/router/pc
• delete restore points
• turn off hibernation (powercfg -h off)
• empty web browser cache
• delete system temp files
• scan Windows for system corruption (sfc /scannow)
• scan drive for file corruption (chkdsk c: /r)
• disable unwanted scheduled tasks
• disable unnecessary startup services
• disable scheduled defragging
• TRIM any SSD's
• turn off Timeline and Activity History, and all things Microsoft Telemetry based
• empty recycle bin
• delete log files and error reports
• remove old Windows Updates files
• cleanup software installer and distribution caches
• delete unwanted programs
• remove any browser extensions
• if connecting via wireless, try ethernet
• pause any online cloud storage synchronising (OneDrive, DropBox)
CCleaner (free version) or Glary Disk Cleaner or the inbuilt cleanmgr command can do most of those points.
ShutUp10 by O&O Software can stop a lot of telemetry items.
other things to try;
• create another user account and login under that profile
• check for firmware updates for modem/router and PC BIOS
do a web speed check - go to
www.speedtest.net and post the results.
has there been any changes in the time frame that the FPS rates have dropped?
like new software or hardware, or extra users on the network?
it could also be performance rot, and doing a fresh install of Windows may help.