Washington state security deposit and written checklist question

[Ana Vhan]

Hello my fellow members, as always I post my question with great hope that you help me with your insights.

We had tenants(4 girls) for a year who just moved out from our  house in Kirkland(Washington state). We have been very sweet to these tenants - we rented them home when they had no credit history, we fixed every problem they reported(and they reported every small thing they noticed), we took care of them when the kitchen was non functional for a couple of days. Throughout the tenancy these tenants have been nothing but bullies and they have tried to take advantage of our goodwill. Now, when they left we noticed that a couple of things broken for which we charged them(garbage disposal $250 and sliding door screen replacement $150). We fee it’s fair. But they are arguing that there is no written checklist at the start of the agreement and thus we cannot retain any money from the deposit. Although we didn’t have a move in move out list at the start of the lease, we have all the communication from the beginning to prove that they reported every issue and we took care of it. What is the checklist they are referring to? We do have a proper lease agreement in place with right terms. Is that not enough? 

We are just so pissed with these girls that they are taking advantage of our nature and this one thing we missed. Is there any work around this? 

TIA. 

Ana