It appears they were on a lease for the year. They've now become month to month tenants.
Pennsylvania state law does not specify how much notice landlords or tenants must provide to end a month-to-month rental agreement, but 30 days is typical. Your rental agreement should provide this information if it doesn't speak to notice, I'd send them a letter (certified, registered, or via FedEx), one by regular US Mail, and I'd post (tack) one on their door.
I'd keep copies for court use, if they don't voluntarily move.
I'd send the testers within the next week, giving them until the end of October to voluntarily vacate.
After the 30 day period has passed, and they haven't moved, you'll have to take them to court and evict them.
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