If so you can change their hostname in the raspi-config file - following process was suggested by G8GKQ, my menu structure was slightly different but you get the idea.
73sudo raspi-config
then select:
2 Network Options
N1 Hostname
Read next screen and OK
Edit hostname, press enter
Tab twice to finish, press enter
Yes to reboot now.
It might take 24 hours or a router reboot for the router (and hence Advanced IP Scanner) to pick up the change.
Noel