Managing social media for 3 clients is slowly killing me. How do people do this at scale?

I want to automate stuff anyone can help here?

I run content for 3 small businesses. That means 3 different brand voices. 3 content calendars. 3 sets of captions. Scheduling. Posting. Monitoring comments.

I work 6 days a week and still feel behind. Every Sunday I spend 4 hours just planning the week ahead.

I started doing this because I thought it would be flexible.

It is the least flexible thing I have ever done. How are solo social media managers handling more than 2 clients without burning out?