Ask yourself what your "job" in the homelab should be: do you want to manage what apps are available or do you want to be a DB admin? Because if you are sharing DB-containers between multiple applications, then you've basically signed up to checking the release notes of each release of each involved app closely to check for changes like this.

Treating "immich+postgres+redis+..." as a single unit that you deploy and upgrade together makes everything simpler at the (probably small) cost of requiring some more resources. But even on a 4GB-ram RPi that's unlikely to become the primary issue soon.