Child support does not automatically go up. You have to ask to modify your child support. The fact that the child is now 12 is a factor. The child support schedule (the table that sets how much should be paid according to the parties' combined monthly incomes) has separate categories for children 0-11 and 12-18. So your child is now in a new category for child support.
If your child support was set administratively (meaning you never went to court for child support) you have to go through Division of Child Support for a modification. Below is a link to the DCS modification page. DCS will contact the ex to get her income information. Even if she doesn't cooperate, DCS can get her income information through Employment Security.
If your child support was set through Superior Court, you can file a modification yourself or go through DCS (if they're collecting support for you). Below is a link to the WA Courts webpage for modification forms. If you do it yourself, you can go faster but you really have to pay close attention to what you're doing. A lot of people find it very frustrating. If you go through DCS, you are at their mercy. You may or may not be at the top of their list of priorities.
Either way, nothing will happen until YOU initiate a modification.
In WA you can modify child support every two years. Because your child is entering those teen years, plan on modifying every two years. Also, if the child will be going to college, you can petition the court for post-secondary support to help with college expenses. You have to do it before child support expires (before graduation or turning 18, whichever happens later).