All sites running slow but Hummingbird breaks sites

I have four sites. Three of them run slowly and I've been trying to work out where the bottlenecks are. Traceroute suggests that server response times are not the issue.

Looking at recommendations from the Hub, improvements should be possible using Hummingbird but when I use the settings suggested it tends to break my sites.

Am I missing something here?

Can someone have a look please and advise on how I can improve things?

I have enabled support access on the three sites: