JQuery :: Bizarre Behavior Caused By $('.classname').change() On Multiple <select>

I have a series of paired <select> objects. By paired I mean the <option> values of one is dependent on the state of the other via an ajax call. Something like:

[Cdoe]..

Here's where the bizarre behavior happens. If I trigger a change event for "primary" classes, i.e. $('.primary').change(), only the LAST "secondary" gets changed. For the list above only $('#number_six') would be dynamically filled. I tried using $('.primary').each(function(){ blah }) instead but got the same result. I read somewhere that some change events are only registered when the object is no longer in focus, so I tried adding .blur() to the end of the statement.