For me it sounds like something with CO2, not getting narced, 20m is just shallow.
Poeple who say stay shallower, that is nice, but I will not be satisfied with a guide that is not diving deeper. If I guide stays at 20m, no problem, I will go to 40 then, and do my own dive. But I know what I am doing.
The problem with being a guide is that you must be able to dive to at least 30m, also inexperienced divers with an aow cert want to do that depths and if something happens, the guide must do his job.
So you must figure out what the reason is.
Have you done some solodiving? How do you feel on doing that? Even if it is just 10m? I think for divemasters it would be a good requirement if they have done some solodives. Then you know how you feel and if you can rescue yourself if needed.
I ask you about solodiving, because is it the responsibility of diving with a group or really just the depth?
Woman seem to become more careful when they get a child and are most times more careful than man. So it can also be something psychological you never are aware of. Did you guide very bad divers? Did something happen on a dive you guided?