It's very common for people to duplicate IPs when logging into social sites whether it's a family checking from one ISP or a large office behind a network. I can't see any reason why that alone would get you flagged.
However if you have shell accounts with no content created to manage things [which is a violation[ you'll want to be more careful and potentially reach out to facebook on that directly less you get considered a fake / fluff account. There is such a thing as an admin only account although they're usually only found with larger advertisers.
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