When I add Denagard to the waterers and start spraying in the water, the bubbles start getting a little brown film over them the more I add the water. When I turn off the water, there are brown spots floating around. I used it last winter, and I don't remember that happening. I tried a few different times, making sure the waterers were clean, using different syringes, etc. and it still does it. The Denagard doesn't expire until 2015, and it was stored at room temperature. Any idea what's up? I didn't feel comfortable giving it to the chickens, so I poured it all out. Need to know whether it's safe or not. Thanks! *Oh, and I thought about adding the Denagard last and stirring it, but I'm still concerned about whether it's safe to use?