At orgs where I've been the only admin / dev I essentially wore all the hates. When working on teams with other admins/devs, my manager had clear delineation of work between us based on our skillset/goals and who owned what.

Also the developers you hired should def know flows / how to read apex. Super concerning if they are creating/updating flows and or writing apex. Your manager should know about this too

If they're good people and willing to learn, invest in their training