Late Rent Payment...need advise.

[Rafiq Merchant]

Hello - I am a newbie to the rental investment area as such could use some advice over here. I have my one and only SFR rented out to this older couple since May of this year. They have been diligently depositing the rent check into my account on the first of every month. However for September she texted me stating that she will deposit the rent on the 3rd. Per the lease terms, rent is considered late after the 3rd so I said okay. However this being the long weekend, the check did not clear completely until the 7th. I do not want to assess any late fees, yet at the same time do not want this to become an issue going forward. They are a nice couple, however do not have good credit yet checked out with their prior landlord. I have a two year lease with them (with 2 months security deposit). Should I talk to them about this or wait for one more month to see if it repeats and take it from there? Any advice will be highly appreciated.