Can a Landlord Charge Late Fees on Top of Late Fees

[Mommyof 2]

My question involves landlord-tenant law in the State of Washington

We were late for a couple of months and we were already aware we would be charged late fees. Well we ended up paying the rent part but not our late fees yet. They posted a 3 day eviction notice on my door for a amount off 300 dollars and my fiance went down to the office and asked what it was for. They told him it was for the late fees and that they were going to start collecting them and charging a 75 dollar late charge for the late fees and 5 dollars a day for just the late fees. Is this at all legal? They just started this as in the month of june. They never brought any of this up during the signing of the lease agreement. I just feel like they are being extremely unfair.

[Mr. Knowitall]

Exactly how are late fees characterized in your lease. Please quote the lease language.