You can also look at your logs. When I've experienced lagginess in the past I would look at Past Logs and scan down the list for errors (usually highlighted in red). 9 times out of 10 there is something screaming for help. Once resolved the hub usually returns to normal.
I had a similar issue, I suggest to contact support and @bobbyD so they can let you know what is the problem, in my case it was a driver flooding my telnet, but by the way, I had the Kasa Manager installed and I deleted it because it was flooding my logs with discoveries of nothing so probably it's flooding your telnet too.
I'm removing Kasa, the Global Cache app and Sonos. I noticed that it couldn't see a couple of sonos devices so was timing out, this is because I set the hub up initially in my office and it discovered the 3 sonos zones there, then i took it home and it found my other 10 at home.
The problem i'm facing now is that it wont let me remove the Sonos app (It just shows a spinning wheel) - potentially because it can't see the office sonos devices. Any tips on a more 'forced' removal?
Pleased to report that it's all super fast again. Will do backups as I install each thing again and will report what it is. So far, it's not looking like it was Sonos as 10 devices installed and all running well.
I feel like going from 2 TP-Link devices to 1 might have helped me now that I think of it...
Ugh maybe I'll switch that puppy to IFTTT control to speed things up... Maybe...
Or open more worm cans in the process...
This helped with my hub performance as well. I changed routers for the purposes of using a VPN and didn't realize I needed to rebuild everything WiFi related. Which as it turns out means to remove and readd all Connect related apps for Sonos, SmartLife, Hue, Lifx because of all the changes the new DHCP did to changing IP addresses.
I also did as @stephack recommends here but didn't realize was to check All logs to watch for any errors. It turns out even though the system was operational it was so slow that I kept troubleshooting symptoms (ie Rules not functioning, devices not reporting, et) and not the real problem of bad apps due to WifI IP changes or drivers. Once I did this the system snapped back to life.
I still need to reserve IP's for devices once I know what best practices are. I think my Hue hub, all my Wifi Sonoff and H801 RGBWW controllers need reserved IP's based on their MAC addresses. I read somewhere @bravenel to not reserve the IP for my HE Hub though because it might interfere with updates notifications. I think I read that @mike.maxwell said it's a good practice to reserve an IP for Sonos devices.