I would integrate with an external spreadsheet (i.e. Google Sheet, SmartSheet, etc.), mirror the data via webhook, then create a Marketo lead that represents each clinic and retrieve + send them their daily delta. (Obviously you may have data privacy concerns that would make an in-house equivalent preferable.)
Otherwise your idea is best -- you can't filter a single Smart List down based on the subscription recipient, you need different SLs and subscriptions.
Cool, thanks as always Sanford!
Just making sure I don't skip any option