I have run into a problem when wet tumbling my brass. I use a solution of tap water, two good squirts of Dawn and a couple of tablespoons of Lemishine. My brass looks fantastic coming out of the tumbler but starts to change color during the rinse. The tarnish is significant as you can see from the photo attached. The tarnished brass is on the right in the photo. There is actually a purple tinge to some of the brass. And it happens to all my brass, not just rifle. This is a recent phenomenon. Any ideas what is causing this? Thanks!