We have already added few Cisco ACI in Entuity but now there is change in Username and Password for these Cisco ACIs.
But when we are trying to modify these devices from device administration page we are getting an option to change the password and not the username.
Do we need to re-add them?
I have replicated this on my 18.0 lab system. Yes, you need to re-add the APIC if the username changes. This issue should be logged by opening a Support ticket.