under WA state landlord tenant act is there a cap on what landlord can charge for late fees

Late Fees: I am still late on last months rent. The late fees are as follows...$50 on the 5th, $15 /day thereafter. I will be paying off the majority of what is owed today, minus about $100. Is there a cap on what a landlord can reasonably charge you for late fees (I figure mine to be at 26.66% to date) and if I've technically paid off my rent, minus late fees, am I still liable for the $15/day late fee? - Is this your question? Add additional information