It depends on how bad things go. Most times, individual sub-domians are managing individual reputation and individual IPs are managing individual reputation. If the things go really sideways or if you are sending email campaigns in a really aggressive or in a really spammy way, the reputation can bleed into other sub-domains.
So, it would be wrong to say it won’t happen, but saying it will happen would be inaccurate as well. This is the case when you ignore problems for a long time, it will be worse for you. But if you notice problems on an individual sub-domain and start to make changes, then you will see that the reputation is typically limited to just that sub-domain.
But again, it is based on the mailbox provider, it is based on how bad things are, but typically the reputations of sub-domains are measured independently.
Here is a good article about how to restore a bad reputation: How to Restore Sender Reputation and Get out of the Spam Folder