How to troubleshoot SER performance

Looking for advice on how to troubleshoot SER performance / LpM. We went from about 150 LpM to about 20 LpM and can’t figure out what has changed. 

There are 12 projects but only 2-3 active. I have around 4,500,000 urls in my identified site list. Proxies seem pretty solid and haven’t changed (I’ve also tried without for short bursts to just check). Internet connection is 100 megabits and I’ve played around with my DNS service just to be sure I’m not rate limited. Use x-evil on two other LAN pcs for captchas. PC is core i7 + 8gb ram.  

When I start SER it just moves slow. CPU is at 1-5%. Can’t figure out what bottleneck to look for!