My landlord turned my account to a collection agency immediately after I moved out. How do I dispute charges?

The charges were upwards of $1000 and ranged from kitchen sink/counter top replacement (~$500) to cleaning *under* the carpet ($150), touch up paint and millwork ($150), utility charges ($200). The receipts that they have shown me had dates that's >6 months before I moved out or no apartment unit-number or date! When I asked them for proof with dates/photos of these, they removed the ~$500 charge for the kitchen but still want to charge for the paint and under-carpet cleaning with no additional proof. While I don't dispute the utility charges, my ask for proof and photos of the others have been met with a "There is no need for further validation.". I did not have to pay any deposits at move-in so there is no deposit to contest. How do I proceed in disputing these charges under RCW laws?