You might want to go look at http://www.deltasociety.com they have a lot of information regarding service animals and what protections you have. That said, Fair Housing is protected on both the State and Federal levels. The Washington State Human Rights Commission will accept complaints for review of Fair Housing issues. You can find them through the State's website at http://www.access.wa.gov
Whether you need to pay a pet deposit for your dogs turns on whether your dogs are service animals. Please review these webpages for some thoughts on that issue. WA does not protect companion animals as service animals are protected. Hope this helps.
I agree with my colleague. If your dogs are actual service dogs, then your landlord usually cannot charge you additional "pet rent" or deposit. You should also contact your city's department of human services for further assistance: http://www.ci.issaquah.wa.us/SectionIndex.asp?SectionID=43