Hi beob
If I understand you correctly, you want to check certificate age for multiple domains that run on the same host?
This may be achieved by creating multiple “Check HTTP service” rules that all apply for the same host.
In each rule you set the “Service name” and “Virtual host” to a unique domain you would like to check.
E.g.
- the webserver is called
webserver-001.provider.intra - you have two domains that are served on this server:
www.somedomain.comandwww.otherdomain.com
The rule for www.somedomain.com could look like this:
The same goes for www.otherdomain.com. You just replace the domain name, of course.
In the end, you will have a list of rules, that all apply to the same webserver but check different domains:
In WATO this will then look something like this (except - it should work at your end 
)
I hope this helps 
Kind regards