Make sure that your custom fields have the correct visibility assigned to them!
Custom fields are an incredibly dynamic way to add more fidelity and user information to profiles. With each field, you can set permission settings to ultimately assign how you want that field to be visible to users in the community. Each permission set is broken down with view access below:
|Community Admins Only||✔️|
|Community Admins & User||✔️|
So, in a use-case where you create a custom field, that that is "user" it will only be visible to the user entering that information in (themselves) and the admin for the community.
If you create a "profile" field, that field is going to be visible to all users in the community.