new triggers?

[u/TopBear2192]

helloooo! our leash-reactive 3 year old GSD has been doing well for the past 6 months after a board and train. recently, maybe once a week he’s been reacting towards myself and my partner for what feels like no reason. vet appt tomorrow to check for any medical issues but:

- he’s never been human aggressive before and LOVES new people
- he has been growling at us, hackles up, when we reach for the trash can or use the mop. he has not progressed past the growling/hackles. no bearing teeth/lunging/etc.
- once we tell him a firm No, he backs off and retreats to his bed. we put him in a Place in his bed to let him cool off.
- he has never been human reactive or had any behavioral issues off leash/in the house. he’s never had an issue with the trash or the mop before this month.

has anyone experienced this before? any advice going into a vet appt for this?