It’s normal if it’s a small company. Big companies have budgets big enough for an entire marketing department in which case all of which you described would be separate jobs for different people but for smaller companies they do expect you to do it all. It should be discussed who is responsible for making the content because in some cases they do expect you to make it. You could always repost tagged photos of the brand but it doesn’t always match the feed theme you’re going for and sometimes it’s not even good quality content. I would just write up a thorough contract stating what specifically your are agreeing to and what is going an extra fee for you. Otherwise they will just ask and ask and ask (for you to do more work).
Ex. You agreed to 5 posts a week to IG and 1 video posted to YouTube. If they wanted two videos made for a week instead one, then make sure to let them know it’s an extra charge of about $300 or so.