As a general rule, unpaid HOA dues are a lien and charge on the property arising from the CC&R's, and without regard to who "owns" the property (and whether the owner is dead or alive). Since a lien can be foreclosed, and if the unit has any substantial equity at all, it would behoove the heirs to pay the dues to avoid interest and legal charges until the unit can be sold.
Your responsibility for the dues will be governed by the law of the state of WA. I don't practice there, and can't comment on that state's law. But I can relate what happened in a Georgia case I recently handled for an association client. You may want to talk to your Probate Attorney about this further.
In the Georgia case, the heirs did basically what you have done. Their parent died intestate, they took what they wanted, and they walked away from the condo. Condo dues until their parent died were paid, so the only amounts unpaid to the association those that came due after the parent died. The bank delayed foreclosure, and the association received nothing for over a year. Under the laws of intestacy in Georgia, the children became the owners immediately on the death of the parent. That went back to the common law of England which required someone to hold title to real property. State law also gave heirs ways to deal with the immediate transfer. They could have renounced the inheritance, and then it woudl not have gone into their name. They could have had an administrator of the intestate estate appointed by the probate court, and then only the estate assets, not the heirs, would have been responsible for the association dues. The heirs in the Georgia case did nothing, so the association successfully sued the heirs as the owners of the property by operation of law. The Georgia Court of Appeals ruled that the association had to be able to collect dues from someone, and since noone other than the intestate heirs (such as a court appointed administrator) was available, the Association could pursue the children by intestate succession. It is likely the associaiton in your situation is pursuing a similar theory. It would behoove you to talk further to your probate attorney to have your personal liability either eliminated or cut off.
I don't enjoy making this type of suggestion, but if you end up being held responsible for the HOA dues and they are substantial, you may want to talk to a different attorney to see if there is a claim that can be made that the probate attorney handled the situation inartfully and might be responsible for any amounts you have to pay to the HOA.
For reference, the Georgia case is Villas at Stone Mountain Condominium v. Blair, 2011 Ga. App. LEXIS 756,*;311 Ga. App. 718; 716 S.E.2d 718;2011
This answer is for general purposes only, and it does not create an attorney-client relationship.