[cypher]

I agree it's not really possible to know just how active they are unless you sit by the cage all night!
How old is your ham now? Even if she isn't old some slow down a bit quicker than others & are a little less active, that & the time of year may explain changes in behaviour.
As long as you get to see her daily so you can tell if she's looking healthy, eating & drinking fine then I wouldn't worry, although we all do!