Reg E Fraud- EFT Claim for Cash App

During a review of the account, we noticed several transactions to Cash App, to the same people from last December and one in January. These were NOT disputed. Should we inquire about these transactions? If so, could we start our calculation from the statement date (plus 60 days) from the statement with the first unauthorized transaction? Does it make a difference that the December, the May and June transactions were on different cards? (The customer has had multiple cards.)