I can't see your lease from where I'm sitting, so I cannot interpret its notice provisions for you. For example, if you agreed that you would be jointly and severally responsible for rent as long as at least one of you remained in residence, then the landlord is correct.

If you notify your landlord that you are no longer paying rent by ACH, and terminate that payment, your landlord will presumably demand the balance of the rent due from you and your roommates and, if not paid by somebody, commence the eviction process.