If your Lutron switches went off-line, that has to be a cloud problem, as there is no direct connection between those switches and your hub. It’s a cloud to cloud integration.
Are the zwave switches marked as running local or in the cloud?
If the Z wave switches are marked as running local something really weird is going on. Try disconnecting the hub from the ethernet and see if the switches are still running slowly. You won’t be able to use them from the app (that requires cloud) but if you have any smart lighting automation set up where One local Switch triggers another local device or a local motion sensor triggers a local switch or you can check those.
If The zwave Switches are marked as running in the cloud, there are two possibilities: that your local Internet is running slow for some reason, or that the SmartThings cloud has a problem with your account.
You can test your local Internet with any speedtest app and see if there’s anything going on there.
If not, it’s an issue with your account on the SmartThings cloud because there’s nothing else that would affect both Lutron switches and Z wave switches. ( well, if your neighbor is a super villain and has an EMP device, but then pretty much everything not connected to SmartThings would be affected as well. )